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Redesign tablesample method API, and do extensive code review. 

The original implementation of TABLESAMPLE modeled the tablesample method
API on index access methods, which wasn't a good choice because, without
specialized DDL commands, there's no way to build an extension that can
implement a TSM.  (Raw inserts into system catalogs are not an acceptable
thing to do, because we can't undo them during DROP EXTENSION, nor will
pg_upgrade behave sanely.)  Instead adopt an API more like procedural
language handlers or foreign data wrappers, wherein the only SQL-level
support object needed is a single handler function identified by having
a special return type.  This lets us get rid of the supporting catalog
altogether, so that no custom DDL support is needed for the feature.

Adjust the API so that it can support non-constant tablesample arguments
(the original coding assumed we could evaluate the argument expressions at
ExecInitSampleScan time, which is undesirable even if it weren't outright
unsafe), and discourage sampling methods from looking at invisible tuples.
Make sure that the BERNOULLI and SYSTEM methods are genuinely repeatable
within and across queries, as required by the SQL standard, and deal more
honestly with methods that can't support that requirement.

Make a full code-review pass over the tablesample additions, and fix
assorted bugs, omissions, infelicities, and cosmetic issues (such as
failure to put the added code stanzas in a consistent ordering).
Improve EXPLAIN's output of tablesample plans, too.

Back-patch to 9.5 so that we don't have to support the original API
in production.
This commit is contained in:
Tom Lane 2015-07-25 14:39:00 -04:00
parent b26e3d660d
commit dd7a8f66ed
83 changed files with 3184 additions and 2589 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
contrib/pg_stat_statements/pg_stat_statements.c
View File

@ -2297,6 +2297,7 @@ JumbleRangeTable(pgssJumbleState *jstate, List *rtable)
{
case RTE_RELATION:
APP_JUMB(rte->relid);
JumbleExpr(jstate, (Node *) rte->tablesample);
break;
case RTE_SUBQUERY:
JumbleQuery(jstate, rte->subquery);
@ -2767,6 +2768,15 @@ JumbleExpr(pgssJumbleState *jstate, Node *node)
JumbleExpr(jstate, rtfunc->funcexpr);
}
break;
case T_TableSampleClause:
{
TableSampleClause *tsc = (TableSampleClause *) node;
APP_JUMB(tsc->tsmhandler);
JumbleExpr(jstate, (Node *) tsc->args);
JumbleExpr(jstate, (Node *) tsc->repeatable);
}
break;
default:
/* Only a warning, since we can stumble along anyway */
elog(WARNING, "unrecognized node type: %d",

4
contrib/tsm_system_rows/Makefile
View File

@ -1,8 +1,8 @@
# src/test/modules/tsm_system_rows/Makefile
# contrib/tsm_system_rows/Makefile
MODULE_big = tsm_system_rows
OBJS = tsm_system_rows.o $(WIN32RES)
PGFILEDESC = "tsm_system_rows - SYSTEM TABLESAMPLE method which accepts number of rows as a limit"
PGFILEDESC = "tsm_system_rows - TABLESAMPLE method which accepts number of rows as a limit"
EXTENSION = tsm_system_rows
DATA = tsm_system_rows--1.0.sql

94
contrib/tsm_system_rows/expected/tsm_system_rows.out
View File

@ -1,31 +1,83 @@
CREATE EXTENSION tsm_system_rows;
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
CREATE TABLE test_tablesample (id int, name text);
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
FROM generate_series(0, 30) s(i);
ANALYZE test_tablesample;
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1000);
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (0);
count
-------
0
(1 row)
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1);
count
-------
1
(1 row)
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (10);
count
-------
10
(1 row)
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (100);
count
-------
31
(1 row)
SELECT id FROM test_tablesample TABLESAMPLE system_rows (8) REPEATABLE (5432);
id
----
7
14
21
28
4
11
18
25
(8 rows)
-- bad parameters should get through planning, but not execution:
EXPLAIN (COSTS OFF)
SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
QUERY PLAN
----------------------------------------
Sample Scan on test_tablesample
Sampling: system_rows ('-1'::bigint)
(2 rows)
EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_rows (20) REPEATABLE (10);
QUERY PLAN
-----------------------------------------------------------------------------------
Sample Scan (system_rows) on test_tablesample (cost=0.00..80.20 rows=20 width=4)
SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
ERROR: sample size must not be negative
-- fail, this method is not repeatable:
SELECT * FROM test_tablesample TABLESAMPLE system_rows (10) REPEATABLE (0);
ERROR: tablesample method system_rows does not support REPEATABLE
LINE 1: SELECT * FROM test_tablesample TABLESAMPLE system_rows (10) ...
^
-- but a join should be allowed:
EXPLAIN (COSTS OFF)
SELECT * FROM
(VALUES (0),(10),(100)) v(nrows),
LATERAL (SELECT count(*) FROM test_tablesample
TABLESAMPLE system_rows (nrows)) ss;
QUERY PLAN
----------------------------------------------------------
Nested Loop
-> Values Scan on "*VALUES*"
-> Aggregate
-> Sample Scan on test_tablesample
Sampling: system_rows ("*VALUES*".column1)
(5 rows)
SELECT * FROM
(VALUES (0),(10),(100)) v(nrows),
LATERAL (SELECT count(*) FROM test_tablesample
TABLESAMPLE system_rows (nrows)) ss;
nrows | count
-------+-------
0 | 0
10 | 10
100 | 31
(3 rows)
CREATE VIEW vv AS
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (20);
SELECT * FROM vv;
count
-------
20
(1 row)
-- done
DROP TABLE test_tablesample CASCADE;
DROP EXTENSION tsm_system_rows; -- fail, view depends on extension
ERROR: cannot drop extension tsm_system_rows because other objects depend on it
DETAIL: view vv depends on function system_rows(internal)
HINT: Use DROP ... CASCADE to drop the dependent objects too.

41
contrib/tsm_system_rows/sql/tsm_system_rows.sql
View File

@ -1,14 +1,39 @@
CREATE EXTENSION tsm_system_rows;
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
CREATE TABLE test_tablesample (id int, name text);
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
FROM generate_series(0, 30) s(i);
ANALYZE test_tablesample;
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1000);
SELECT id FROM test_tablesample TABLESAMPLE system_rows (8) REPEATABLE (5432);
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (0);
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1);
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (10);
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (100);
EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_rows (20) REPEATABLE (10);
-- bad parameters should get through planning, but not execution:
EXPLAIN (COSTS OFF)
SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
-- done
DROP TABLE test_tablesample CASCADE;
SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
-- fail, this method is not repeatable:
SELECT * FROM test_tablesample TABLESAMPLE system_rows (10) REPEATABLE (0);
-- but a join should be allowed:
EXPLAIN (COSTS OFF)
SELECT * FROM
(VALUES (0),(10),(100)) v(nrows),
LATERAL (SELECT count(*) FROM test_tablesample
TABLESAMPLE system_rows (nrows)) ss;
SELECT * FROM
(VALUES (0),(10),(100)) v(nrows),
LATERAL (SELECT count(*) FROM test_tablesample
TABLESAMPLE system_rows (nrows)) ss;
CREATE VIEW vv AS
SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (20);
SELECT * FROM vv;
DROP EXTENSION tsm_system_rows; -- fail, view depends on extension

43
contrib/tsm_system_rows/tsm_system_rows--1.0.sql
View File

@ -1,44 +1,9 @@
/* src/test/modules/tablesample/tsm_system_rows--1.0.sql */
/* contrib/tsm_system_rows/tsm_system_rows--1.0.sql */
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION tsm_system_rows" to load this file. \quit
CREATE FUNCTION tsm_system_rows_init(internal, int4, int4)
RETURNS void
AS 'MODULE_PATHNAME'
CREATE FUNCTION system_rows(internal)
RETURNS tsm_handler
AS 'MODULE_PATHNAME', 'tsm_system_rows_handler'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_rows_nextblock(internal)
RETURNS int4
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_rows_nexttuple(internal, int4, int2)
RETURNS int2
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_rows_examinetuple(internal, int4, internal, bool)
RETURNS bool
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_rows_end(internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_rows_reset(internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_rows_cost(internal, internal, internal, internal, internal, internal, internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
INSERT INTO pg_tablesample_method VALUES('system_rows', false, true,
'tsm_system_rows_init', 'tsm_system_rows_nextblock',
'tsm_system_rows_nexttuple', 'tsm_system_rows_examinetuple',
'tsm_system_rows_end', 'tsm_system_rows_reset', 'tsm_system_rows_cost');

459
contrib/tsm_system_rows/tsm_system_rows.c
View File

@ -1,240 +1,356 @@
/*-------------------------------------------------------------------------
*
* tsm_system_rows.c
* interface routines for system_rows tablesample method
* support routines for SYSTEM_ROWS tablesample method
*
* The desire here is to produce a random sample with a given number of rows
* (or the whole relation, if that is fewer rows). We use a block-sampling
* approach. To ensure that the whole relation will be visited if necessary,
* we start at a randomly chosen block and then advance with a stride that
* is randomly chosen but is relatively prime to the relation's nblocks.
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Because of the dependence on nblocks, this method cannot be repeatable
* across queries. (Even if the user hasn't explicitly changed the relation,
* maintenance activities such as autovacuum might change nblocks.) However,
* we can at least make it repeatable across scans, by determining the
* sampling pattern only once on the first scan. This means that rescans
* won't visit blocks added after the first scan, but that is fine since
* such blocks shouldn't contain any visible tuples anyway.
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* contrib/tsm_system_rows_rowlimit/tsm_system_rows.c
* contrib/tsm_system_rows/tsm_system_rows.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "fmgr.h"
#include "access/tablesample.h"
#include "access/relscan.h"
#include "access/tsmapi.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "nodes/execnodes.h"
#include "nodes/relation.h"
#include "optimizer/clauses.h"
#include "storage/bufmgr.h"
#include "optimizer/cost.h"
#include "utils/sampling.h"
PG_MODULE_MAGIC;
/*
* State
*/
PG_FUNCTION_INFO_V1(tsm_system_rows_handler);
/* Private state */
typedef struct
{
SamplerRandomState randstate;
uint32 seed; /* random seed */
BlockNumber nblocks; /* number of block in relation */
int32 ntuples; /* number of tuples to return */
int32 donetuples; /* tuples already returned */
int64 ntuples; /* number of tuples to return */
int64 donetuples; /* number of tuples already returned */
OffsetNumber lt; /* last tuple returned from current block */
BlockNumber step; /* step size */
BlockNumber doneblocks; /* number of already-scanned blocks */
BlockNumber lb; /* last block visited */
BlockNumber doneblocks; /* number of already returned blocks */
} SystemSamplerData;
PG_FUNCTION_INFO_V1(tsm_system_rows_init);
PG_FUNCTION_INFO_V1(tsm_system_rows_nextblock);
PG_FUNCTION_INFO_V1(tsm_system_rows_nexttuple);
PG_FUNCTION_INFO_V1(tsm_system_rows_examinetuple);
PG_FUNCTION_INFO_V1(tsm_system_rows_end);
PG_FUNCTION_INFO_V1(tsm_system_rows_reset);
PG_FUNCTION_INFO_V1(tsm_system_rows_cost);
/* these three values are not changed during a rescan: */
BlockNumber nblocks; /* number of blocks in relation */
BlockNumber firstblock; /* first block to sample from */
BlockNumber step; /* step size, or 0 if not set yet */
} SystemRowsSamplerData;
static void system_rows_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
static void system_rows_initsamplescan(SampleScanState *node,
int eflags);
static void system_rows_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
static BlockNumber system_rows_nextsampleblock(SampleScanState *node);
static OffsetNumber system_rows_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
static bool SampleOffsetVisible(OffsetNumber tupoffset, HeapScanDesc scan);
static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
/*
* Initializes the state.
* Create a TsmRoutine descriptor for the SYSTEM_ROWS method.
*/
Datum
tsm_system_rows_init(PG_FUNCTION_ARGS)
tsm_system_rows_handler(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
uint32 seed = PG_GETARG_UINT32(1);
int32 ntuples = PG_ARGISNULL(2) ? -1 : PG_GETARG_INT32(2);
HeapScanDesc scan = tsdesc->heapScan;
SystemSamplerData *sampler;
TsmRoutine *tsm = makeNode(TsmRoutine);
if (ntuples < 1)
tsm->parameterTypes = list_make1_oid(INT8OID);
/* See notes at head of file */
tsm->repeatable_across_queries = false;
tsm->repeatable_across_scans = true;
tsm->SampleScanGetSampleSize = system_rows_samplescangetsamplesize;
tsm->InitSampleScan = system_rows_initsamplescan;
tsm->BeginSampleScan = system_rows_beginsamplescan;
tsm->NextSampleBlock = system_rows_nextsampleblock;
tsm->NextSampleTuple = system_rows_nextsampletuple;
tsm->EndSampleScan = NULL;
PG_RETURN_POINTER(tsm);
}
/*
* Sample size estimation.
*/
static void
system_rows_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples)
{
Node *limitnode;
int64 ntuples;
double npages;
/* Try to extract an estimate for the limit rowcount */
limitnode = (Node *) linitial(paramexprs);
limitnode = estimate_expression_value(root, limitnode);
if (IsA(limitnode, Const) &&
!((Const *) limitnode)->constisnull)
{
ntuples = DatumGetInt64(((Const *) limitnode)->constvalue);
if (ntuples < 0)
{
/* Default ntuples if the value is bogus */
ntuples = 1000;
}
}
else
{
/* Default ntuples if we didn't obtain a non-null Const */
ntuples = 1000;
}
/* Clamp to the estimated relation size */
if (ntuples > baserel->tuples)
ntuples = (int64) baserel->tuples;
ntuples = clamp_row_est(ntuples);
if (baserel->tuples > 0 && baserel->pages > 0)
{
/* Estimate number of pages visited based on tuple density */
double density = baserel->tuples / (double) baserel->pages;
npages = ntuples / density;
}
else
{
/* For lack of data, assume one tuple per page */
npages = ntuples;
}
/* Clamp to sane value */
npages = clamp_row_est(Min((double) baserel->pages, npages));
*pages = npages;
*tuples = ntuples;
}
/*
* Initialize during executor setup.
*/
static void
system_rows_initsamplescan(SampleScanState *node, int eflags)
{
node->tsm_state = palloc0(sizeof(SystemRowsSamplerData));
/* Note the above leaves tsm_state->step equal to zero */
}
/*
* Examine parameters and prepare for a sample scan.
*/
static void
system_rows_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed)
{
SystemRowsSamplerData *sampler = (SystemRowsSamplerData *) node->tsm_state;
int64 ntuples = DatumGetInt64(params[0]);
if (ntuples < 0)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("invalid sample size"),
errhint("Sample size must be positive integer value.")));
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
errmsg("sample size must not be negative")));
sampler = palloc0(sizeof(SystemSamplerData));
/* Remember initial values for reinit */
sampler->seed = seed;
sampler->nblocks = scan->rs_nblocks;
sampler->ntuples = ntuples;
sampler->donetuples = 0;
sampler->lt = InvalidOffsetNumber;
sampler->doneblocks = 0;
sampler_random_init_state(sampler->seed, sampler->randstate);
/* Find relative prime as step size for linear probing. */
sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
/* lb will be initialized during first NextSampleBlock call */
/* we intentionally do not change nblocks/firstblock/step here */
/*
* Randomize start position so that blocks close to step size don't have
* higher probability of being chosen on very short scan.
* We *must* use pagemode visibility checking in this module, so force
* that even though it's currently default.
*/
sampler->lb = sampler_random_fract(sampler->randstate) *
(sampler->nblocks / sampler->step);
tsdesc->tsmdata = (void *) sampler;
PG_RETURN_VOID();
node->use_pagemode = true;
}
/*
* Get next block number or InvalidBlockNumber when we're done.
* Select next block to sample.
*
* Uses linear probing algorithm for picking next block.
*/
Datum
tsm_system_rows_nextblock(PG_FUNCTION_ARGS)
static BlockNumber
system_rows_nextsampleblock(SampleScanState *node)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
SystemRowsSamplerData *sampler = (SystemRowsSamplerData *) node->tsm_state;
HeapScanDesc scan = node->ss.ss_currentScanDesc;
sampler->lb = (sampler->lb + sampler->step) % sampler->nblocks;
sampler->doneblocks++;
/* First call within scan? */
if (sampler->doneblocks == 0)
{
/* First scan within query? */
if (sampler->step == 0)
{
/* Initialize now that we have scan descriptor */
SamplerRandomState randstate;
/* All blocks have been read, we're done */
if (sampler->doneblocks > sampler->nblocks ||
/* If relation is empty, there's nothing to scan */
if (scan->rs_nblocks == 0)
return InvalidBlockNumber;
/* We only need an RNG during this setup step */
sampler_random_init_state(sampler->seed, randstate);
/* Compute nblocks/firstblock/step only once per query */
sampler->nblocks = scan->rs_nblocks;
/* Choose random starting block within the relation */
/* (Actually this is the predecessor of the first block visited) */
sampler->firstblock = sampler_random_fract(randstate) *
sampler->nblocks;
/* Find relative prime as step size for linear probing */
sampler->step = random_relative_prime(sampler->nblocks, randstate);
}
/* Reinitialize lb */
sampler->lb = sampler->firstblock;
}
/* If we've read all blocks or returned all needed tuples, we're done */
if (++sampler->doneblocks > sampler->nblocks ||
sampler->donetuples >= sampler->ntuples)
PG_RETURN_UINT32(InvalidBlockNumber);
return InvalidBlockNumber;
PG_RETURN_UINT32(sampler->lb);
/*
* It's probably impossible for scan->rs_nblocks to decrease between scans
* within a query; but just in case, loop until we select a block number
* less than scan->rs_nblocks. We don't care if scan->rs_nblocks has
* increased since the first scan.
*/
do
{
/* Advance lb, using uint64 arithmetic to forestall overflow */
sampler->lb = ((uint64) sampler->lb + sampler->step) % sampler->nblocks;
} while (sampler->lb >= scan->rs_nblocks);
return sampler->lb;
}
/*
* Get next tuple offset in current block or InvalidOffsetNumber if we are done
* with this block.
* Select next sampled tuple in current block.
*
* In block sampling, we just want to sample all the tuples in each selected
* block.
*
* When we reach end of the block, return InvalidOffsetNumber which tells
* SampleScan to go to next block.
*/
Datum
tsm_system_rows_nexttuple(PG_FUNCTION_ARGS)
static OffsetNumber
system_rows_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
OffsetNumber maxoffset = PG_GETARG_UINT16(2);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
SystemRowsSamplerData *sampler = (SystemRowsSamplerData *) node->tsm_state;
HeapScanDesc scan = node->ss.ss_currentScanDesc;
OffsetNumber tupoffset = sampler->lt;
if (tupoffset == InvalidOffsetNumber)
tupoffset = FirstOffsetNumber;
else
tupoffset++;
/* Quit if we've returned all needed tuples */
if (sampler->donetuples >= sampler->ntuples)
return InvalidOffsetNumber;
if (tupoffset > maxoffset ||
sampler->donetuples >= sampler->ntuples)
tupoffset = InvalidOffsetNumber;
/*
* Because we should only count visible tuples as being returned, we need
* to search for a visible tuple rather than just let the core code do it.
*/
/* We rely on the data accumulated in pagemode access */
Assert(scan->rs_pageatatime);
for (;;)
{
/* Advance to next possible offset on page */
if (tupoffset == InvalidOffsetNumber)
tupoffset = FirstOffsetNumber;
else
tupoffset++;
/* Done? */
if (tupoffset > maxoffset)
{
tupoffset = InvalidOffsetNumber;
break;
}
/* Found a candidate? */
if (SampleOffsetVisible(tupoffset, scan))
{
sampler->donetuples++;
break;
}
}
sampler->lt = tupoffset;
PG_RETURN_UINT16(tupoffset);
return tupoffset;
}
/*
* Examine tuple and decide if it should be returned.
* Check if tuple offset is visible
*
* In pageatatime mode, heapgetpage() already did visibility checks,
* so just look at the info it left in rs_vistuples[].
*/
Datum
tsm_system_rows_examinetuple(PG_FUNCTION_ARGS)
static bool
SampleOffsetVisible(OffsetNumber tupoffset, HeapScanDesc scan)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
bool visible = PG_GETARG_BOOL(3);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
int start = 0,
end = scan->rs_ntuples - 1;
if (!visible)
PG_RETURN_BOOL(false);
sampler->donetuples++;
PG_RETURN_BOOL(true);
}
/*
* Cleanup method.
*/
Datum
tsm_system_rows_end(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
pfree(tsdesc->tsmdata);
PG_RETURN_VOID();
}
/*
* Reset state (called by ReScan).
*/
Datum
tsm_system_rows_reset(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
sampler->lt = InvalidOffsetNumber;
sampler->donetuples = 0;
sampler->doneblocks = 0;
sampler_random_init_state(sampler->seed, sampler->randstate);
sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
sampler->lb = sampler_random_fract(sampler->randstate) * (sampler->nblocks / sampler->step);
PG_RETURN_VOID();
}
/*
* Costing function.
*/
Datum
tsm_system_rows_cost(PG_FUNCTION_ARGS)
{
PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
Path *path = (Path *) PG_GETARG_POINTER(1);
RelOptInfo *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
List *args = (List *) PG_GETARG_POINTER(3);
BlockNumber *pages = (BlockNumber *) PG_GETARG_POINTER(4);
double *tuples = (double *) PG_GETARG_POINTER(5);
Node *limitnode;
int32 ntuples;
limitnode = linitial(args);
limitnode = estimate_expression_value(root, limitnode);
if (IsA(limitnode, RelabelType))
limitnode = (Node *) ((RelabelType *) limitnode)->arg;
if (IsA(limitnode, Const))
ntuples = DatumGetInt32(((Const *) limitnode)->constvalue);
else
while (start <= end)
{
/* Default ntuples if the estimation didn't return Const. */
ntuples = 1000;
int mid = (start + end) / 2;
OffsetNumber curoffset = scan->rs_vistuples[mid];
if (tupoffset == curoffset)
return true;
else if (tupoffset < curoffset)
end = mid - 1;
else
start = mid + 1;
}
*pages = Min(baserel->pages, ntuples);
*tuples = ntuples;
path->rows = *tuples;
PG_RETURN_VOID();
return false;
}
/*
* Compute greatest common divisor of two uint32's.
*/
static uint32
gcd(uint32 a, uint32 b)
{
@ -250,22 +366,29 @@ gcd(uint32 a, uint32 b)
return b;
}
/*
* Pick a random value less than and relatively prime to n, if possible
* (else return 1).
*/
static uint32
random_relative_prime(uint32 n, SamplerRandomState randstate)
{
/* Pick random starting number, with some limits on what it can be. */
uint32 r = (uint32) sampler_random_fract(randstate) * n / 2 + n / 4,
t;
uint32 r;
/* Safety check to avoid infinite loop or zero result for small n. */
if (n <= 1)
return 1;
/*
* This should only take 2 or 3 iterations as the probability of 2 numbers
* being relatively prime is ~61%.
* being relatively prime is ~61%; but just in case, we'll include a
* CHECK_FOR_INTERRUPTS in the loop.
*/
while ((t = gcd(r, n)) > 1)
do
{
CHECK_FOR_INTERRUPTS();
r /= t;
}
r = (uint32) (sampler_random_fract(randstate) * n);
} while (r == 0 || gcd(r, n) > 1);
return r;
}

2
contrib/tsm_system_rows/tsm_system_rows.control
View File

@ -1,5 +1,5 @@
# tsm_system_rows extension
comment = 'SYSTEM TABLESAMPLE method which accepts number rows as a limit'
comment = 'TABLESAMPLE method which accepts number of rows as a limit'
default_version = '1.0'
module_pathname = '$libdir/tsm_system_rows'
relocatable = true

4
contrib/tsm_system_time/Makefile
View File

@ -1,8 +1,8 @@
# src/test/modules/tsm_system_time/Makefile
# contrib/tsm_system_time/Makefile
MODULE_big = tsm_system_time
OBJS = tsm_system_time.o $(WIN32RES)
PGFILEDESC = "tsm_system_time - SYSTEM TABLESAMPLE method which accepts number rows of as a limit"
PGFILEDESC = "tsm_system_time - TABLESAMPLE method which accepts time in milliseconds as a limit"
EXTENSION = tsm_system_time
DATA = tsm_system_time--1.0.sql

136
contrib/tsm_system_time/expected/tsm_system_time.out
View File

@ -1,54 +1,100 @@
CREATE EXTENSION tsm_system_time;
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
CREATE TABLE test_tablesample (id int, name text);
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
FROM generate_series(0, 30) s(i);
ANALYZE test_tablesample;
SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (1000);
-- It's a bit tricky to test SYSTEM_TIME in a platform-independent way.
-- We can test the zero-time corner case ...
SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (0);
count
-------
0
(1 row)
-- ... and we assume that this will finish before running out of time:
SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (100000);
count
-------
31
(1 row)
SELECT id FROM test_tablesample TABLESAMPLE system_time (1000) REPEATABLE (5432);
id
----
7
14
21
28
4
11
18
25
1
8
15
22
29
5
12
19
26
2
9
16
23
30
6
13
20
27
3
10
17
24
0
(31 rows)
-- bad parameters should get through planning, but not execution:
EXPLAIN (COSTS OFF)
SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
QUERY PLAN
--------------------------------------------------
Sample Scan on test_tablesample
Sampling: system_time ('-1'::double precision)
(2 rows)
EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_time (100) REPEATABLE (10);
QUERY PLAN
------------------------------------------------------------------------------------
Sample Scan (system_time) on test_tablesample (cost=0.00..100.25 rows=25 width=4)
(1 row)
SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
ERROR: sample collection time must not be negative
-- fail, this method is not repeatable:
SELECT * FROM test_tablesample TABLESAMPLE system_time (10) REPEATABLE (0);
ERROR: tablesample method system_time does not support REPEATABLE
LINE 1: SELECT * FROM test_tablesample TABLESAMPLE system_time (10) ...
^
-- since it's not repeatable, we expect a Materialize node in these plans:
EXPLAIN (COSTS OFF)
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (100000)) ss;
QUERY PLAN
------------------------------------------------------------------------
Nested Loop
-> Aggregate
-> Materialize
-> Sample Scan on test_tablesample
Sampling: system_time ('100000'::double precision)
-> Values Scan on "*VALUES*"
(6 rows)
-- done
DROP TABLE test_tablesample CASCADE;
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (100000)) ss;
time | count
--------+-------
0 | 31
100000 | 31
(2 rows)
EXPLAIN (COSTS OFF)
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (time)) ss;
QUERY PLAN
----------------------------------------------------------------
Nested Loop
-> Values Scan on "*VALUES*"
-> Aggregate
-> Materialize
-> Sample Scan on test_tablesample
Sampling: system_time ("*VALUES*".column1)
(6 rows)
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (time)) ss;
time | count
--------+-------
0 | 0
100000 | 31
(2 rows)
CREATE VIEW vv AS
SELECT * FROM test_tablesample TABLESAMPLE system_time (20);
EXPLAIN (COSTS OFF) SELECT * FROM vv;
QUERY PLAN
--------------------------------------------------
Sample Scan on test_tablesample
Sampling: system_time ('20'::double precision)
(2 rows)
DROP EXTENSION tsm_system_time; -- fail, view depends on extension
ERROR: cannot drop extension tsm_system_time because other objects depend on it
DETAIL: view vv depends on function system_time(internal)
HINT: Use DROP ... CASCADE to drop the dependent objects too.

53
contrib/tsm_system_time/sql/tsm_system_time.sql
View File

@ -1,14 +1,51 @@
CREATE EXTENSION tsm_system_time;
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
CREATE TABLE test_tablesample (id int, name text);
INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
FROM generate_series(0, 30) s(i);
ANALYZE test_tablesample;
SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (1000);
SELECT id FROM test_tablesample TABLESAMPLE system_time (1000) REPEATABLE (5432);
-- It's a bit tricky to test SYSTEM_TIME in a platform-independent way.
-- We can test the zero-time corner case ...
SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (0);
-- ... and we assume that this will finish before running out of time:
SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (100000);
EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_time (100) REPEATABLE (10);
-- bad parameters should get through planning, but not execution:
EXPLAIN (COSTS OFF)
SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
-- done
DROP TABLE test_tablesample CASCADE;
SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
-- fail, this method is not repeatable:
SELECT * FROM test_tablesample TABLESAMPLE system_time (10) REPEATABLE (0);
-- since it's not repeatable, we expect a Materialize node in these plans:
EXPLAIN (COSTS OFF)
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (100000)) ss;
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (100000)) ss;
EXPLAIN (COSTS OFF)
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (time)) ss;
SELECT * FROM
(VALUES (0),(100000)) v(time),
LATERAL (SELECT COUNT(*) FROM test_tablesample
TABLESAMPLE system_time (time)) ss;
CREATE VIEW vv AS
SELECT * FROM test_tablesample TABLESAMPLE system_time (20);
EXPLAIN (COSTS OFF) SELECT * FROM vv;
DROP EXTENSION tsm_system_time; -- fail, view depends on extension

38
contrib/tsm_system_time/tsm_system_time--1.0.sql
View File

@ -1,39 +1,9 @@
/* src/test/modules/tablesample/tsm_system_time--1.0.sql */
/* contrib/tsm_system_time/tsm_system_time--1.0.sql */
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION tsm_system_time" to load this file. \quit
CREATE FUNCTION tsm_system_time_init(internal, int4, int4)
RETURNS void
AS 'MODULE_PATHNAME'
CREATE FUNCTION system_time(internal)
RETURNS tsm_handler
AS 'MODULE_PATHNAME', 'tsm_system_time_handler'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_time_nextblock(internal)
RETURNS int4
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_time_nexttuple(internal, int4, int2)
RETURNS int2
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_time_end(internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_time_reset(internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
CREATE FUNCTION tsm_system_time_cost(internal, internal, internal, internal, internal, internal, internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
INSERT INTO pg_tablesample_method VALUES('system_time', false, true,
'tsm_system_time_init', 'tsm_system_time_nextblock',
'tsm_system_time_nexttuple', '-', 'tsm_system_time_end',
'tsm_system_time_reset', 'tsm_system_time_cost');

499
contrib/tsm_system_time/tsm_system_time.c
View File

@ -1,286 +1,320 @@
/*-------------------------------------------------------------------------
*
* tsm_system_time.c
* interface routines for system_time tablesample method
* support routines for SYSTEM_TIME tablesample method
*
* The desire here is to produce a random sample with as many rows as possible
* in no more than the specified amount of time. We use a block-sampling
* approach. To ensure that the whole relation will be visited if necessary,
* we start at a randomly chosen block and then advance with a stride that
* is randomly chosen but is relatively prime to the relation's nblocks.
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Because of the time dependence, this method is necessarily unrepeatable.
* However, we do what we can to reduce surprising behavior by selecting
* the sampling pattern just once per query, much as in tsm_system_rows.
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* contrib/tsm_system_time_rowlimit/tsm_system_time.c
* contrib/tsm_system_time/tsm_system_time.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "fmgr.h"
#ifdef _MSC_VER
#include <float.h> /* for _isnan */
#endif
#include <math.h>
#include "access/tablesample.h"
#include "access/relscan.h"
#include "access/tsmapi.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "nodes/execnodes.h"
#include "nodes/relation.h"
#include "optimizer/clauses.h"
#include "storage/bufmgr.h"
#include "optimizer/cost.h"
#include "utils/sampling.h"
#include "utils/spccache.h"
#include "utils/timestamp.h"
PG_MODULE_MAGIC;
/*
* State
*/
PG_FUNCTION_INFO_V1(tsm_system_time_handler);
/* Private state */
typedef struct
{
SamplerRandomState randstate;
uint32 seed; /* random seed */
BlockNumber nblocks; /* number of block in relation */
int32 time; /* time limit for sampling */
TimestampTz start_time; /* start time of sampling */
TimestampTz end_time; /* end time of sampling */
double millis; /* time limit for sampling */
instr_time start_time; /* scan start time */
OffsetNumber lt; /* last tuple returned from current block */
BlockNumber step; /* step size */
BlockNumber doneblocks; /* number of already-scanned blocks */
BlockNumber lb; /* last block visited */
BlockNumber estblocks; /* estimated number of returned blocks
* (moving) */
BlockNumber doneblocks; /* number of already returned blocks */
} SystemSamplerData;
PG_FUNCTION_INFO_V1(tsm_system_time_init);
PG_FUNCTION_INFO_V1(tsm_system_time_nextblock);
PG_FUNCTION_INFO_V1(tsm_system_time_nexttuple);
PG_FUNCTION_INFO_V1(tsm_system_time_end);
PG_FUNCTION_INFO_V1(tsm_system_time_reset);
PG_FUNCTION_INFO_V1(tsm_system_time_cost);
/* these three values are not changed during a rescan: */
BlockNumber nblocks; /* number of blocks in relation */
BlockNumber firstblock; /* first block to sample from */
BlockNumber step; /* step size, or 0 if not set yet */
} SystemTimeSamplerData;
static void system_time_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
static void system_time_initsamplescan(SampleScanState *node,
int eflags);
static void system_time_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
static BlockNumber system_time_nextsampleblock(SampleScanState *node);
static OffsetNumber system_time_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
/*
* Initializes the state.
* Create a TsmRoutine descriptor for the SYSTEM_TIME method.
*/
Datum
tsm_system_time_init(PG_FUNCTION_ARGS)
tsm_system_time_handler(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
uint32 seed = PG_GETARG_UINT32(1);
int32 time = PG_ARGISNULL(2) ? -1 : PG_GETARG_INT32(2);
HeapScanDesc scan = tsdesc->heapScan;
SystemSamplerData *sampler;
TsmRoutine *tsm = makeNode(TsmRoutine);
if (time < 1)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("invalid time limit"),
errhint("Time limit must be positive integer value.")));
tsm->parameterTypes = list_make1_oid(FLOAT8OID);
sampler = palloc0(sizeof(SystemSamplerData));
/* See notes at head of file */
tsm->repeatable_across_queries = false;
tsm->repeatable_across_scans = false;
/* Remember initial values for reinit */
sampler->seed = seed;
sampler->nblocks = scan->rs_nblocks;
sampler->lt = InvalidOffsetNumber;
sampler->estblocks = 2;
sampler->doneblocks = 0;
sampler->time = time;
sampler->start_time = GetCurrentTimestamp();
sampler->end_time = TimestampTzPlusMilliseconds(sampler->start_time,
sampler->time);
tsm->SampleScanGetSampleSize = system_time_samplescangetsamplesize;
tsm->InitSampleScan = system_time_initsamplescan;
tsm->BeginSampleScan = system_time_beginsamplescan;
tsm->NextSampleBlock = system_time_nextsampleblock;
tsm->NextSampleTuple = system_time_nextsampletuple;
tsm->EndSampleScan = NULL;
sampler_random_init_state(sampler->seed, sampler->randstate);
/* Find relative prime as step size for linear probing. */
sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
/*
* Randomize start position so that blocks close to step size don't have
* higher probability of being chosen on very short scan.
*/
sampler->lb = sampler_random_fract(sampler->randstate) * (sampler->nblocks / sampler->step);
tsdesc->tsmdata = (void *) sampler;
PG_RETURN_VOID();
PG_RETURN_POINTER(tsm);
}
/*
* Get next block number or InvalidBlockNumber when we're done.
*
* Uses linear probing algorithm for picking next block.
* Sample size estimation.
*/
Datum
tsm_system_time_nextblock(PG_FUNCTION_ARGS)
static void
system_time_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
sampler->lb = (sampler->lb + sampler->step) % sampler->nblocks;
sampler->doneblocks++;
/* All blocks have been read, we're done */
if (sampler->doneblocks > sampler->nblocks)
PG_RETURN_UINT32(InvalidBlockNumber);
/*
* Update the estimations for time limit at least 10 times per estimated
* number of returned blocks to handle variations in block read speed.
*/
if (sampler->doneblocks % Max(sampler->estblocks / 10, 1) == 0)
{
TimestampTz now = GetCurrentTimestamp();
long secs;
int usecs;
int usecs_remaining;
int time_per_block;
TimestampDifference(sampler->start_time, now, &secs, &usecs);
usecs += (int) secs *1000000;
time_per_block = usecs / sampler->doneblocks;
/* No time left, end. */
TimestampDifference(now, sampler->end_time, &secs, &usecs);
if (secs <= 0 && usecs <= 0)
PG_RETURN_UINT32(InvalidBlockNumber);
/* Remaining microseconds */
usecs_remaining = usecs + (int) secs *1000000;
/* Recalculate estimated returned number of blocks */
if (time_per_block < usecs_remaining && time_per_block > 0)
sampler->estblocks = sampler->time * time_per_block;
}
PG_RETURN_UINT32(sampler->lb);
}
/*
* Get next tuple offset in current block or InvalidOffsetNumber if we are done
* with this block.
*/
Datum
tsm_system_time_nexttuple(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
OffsetNumber maxoffset = PG_GETARG_UINT16(2);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
OffsetNumber tupoffset = sampler->lt;
if (tupoffset == InvalidOffsetNumber)
tupoffset = FirstOffsetNumber;
else
tupoffset++;
if (tupoffset > maxoffset)
tupoffset = InvalidOffsetNumber;
sampler->lt = tupoffset;
PG_RETURN_UINT16(tupoffset);
}
/*
* Cleanup method.
*/
Datum
tsm_system_time_end(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
pfree(tsdesc->tsmdata);
PG_RETURN_VOID();
}
/*
* Reset state (called by ReScan).
*/
Datum
tsm_system_time_reset(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
sampler->lt = InvalidOffsetNumber;
sampler->start_time = GetCurrentTimestamp();
sampler->end_time = TimestampTzPlusMilliseconds(sampler->start_time,
sampler->time);
sampler->estblocks = 2;
sampler->doneblocks = 0;
sampler_random_init_state(sampler->seed, sampler->randstate);
sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
sampler->lb = sampler_random_fract(sampler->randstate) * (sampler->nblocks / sampler->step);
PG_RETURN_VOID();
}
/*
* Costing function.
*/
Datum
tsm_system_time_cost(PG_FUNCTION_ARGS)
{
PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
Path *path = (Path *) PG_GETARG_POINTER(1);
RelOptInfo *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
List *args = (List *) PG_GETARG_POINTER(3);
BlockNumber *pages = (BlockNumber *) PG_GETARG_POINTER(4);
double *tuples = (double *) PG_GETARG_POINTER(5);
Node *limitnode;
int32 time;
BlockNumber relpages;
double reltuples;
double density;
double millis;
double spc_random_page_cost;
double npages;
double ntuples;
limitnode = linitial(args);
/* Try to extract an estimate for the limit time spec */
limitnode = (Node *) linitial(paramexprs);
limitnode = estimate_expression_value(root, limitnode);
if (IsA(limitnode, RelabelType))
limitnode = (Node *) ((RelabelType *) limitnode)->arg;
if (IsA(limitnode, Const))
time = DatumGetInt32(((Const *) limitnode)->constvalue);
if (IsA(limitnode, Const) &&
!((Const *) limitnode)->constisnull)
{
millis = DatumGetFloat8(((Const *) limitnode)->constvalue);
if (millis < 0 || isnan(millis))
{
/* Default millis if the value is bogus */
millis = 1000;
}
}
else
{
/* Default time (1s) if the estimation didn't return Const. */
time = 1000;
/* Default millis if we didn't obtain a non-null Const */
millis = 1000;
}
relpages = baserel->pages;
reltuples = baserel->tuples;
/* estimate the tuple density */
if (relpages > 0)
density = reltuples / (double) relpages;
else
density = (BLCKSZ - SizeOfPageHeaderData) / baserel->width;
/*
* We equal random page cost value to number of ms it takes to read the
* random page here which is far from accurate but we don't have anything
* better to base our predicted page reads.
*/
/* Get the planner's idea of cost per page read */
get_tablespace_page_costs(baserel->reltablespace,
&spc_random_page_cost,
NULL);
/*
* Assumption here is that we'll never read less than 1% of table pages,
* this is here mainly because it is much less bad to overestimate than
* underestimate and using just spc_random_page_cost will probably lead to
* underestimations in general.
* Estimate the number of pages we can read by assuming that the cost
* figure is expressed in milliseconds. This is completely, unmistakably
* bogus, but we have to do something to produce an estimate and there's
* no better answer.
*/
*pages = Min(baserel->pages, Max(time / spc_random_page_cost, baserel->pages / 100));
*tuples = rint(density * (double) *pages * path->rows / baserel->tuples);
path->rows = *tuples;
if (spc_random_page_cost > 0)
npages = millis / spc_random_page_cost;
else
npages = millis; /* even more bogus, but whatcha gonna do? */
PG_RETURN_VOID();
/* Clamp to sane value */
npages = clamp_row_est(Min((double) baserel->pages, npages));
if (baserel->tuples > 0 && baserel->pages > 0)
{
/* Estimate number of tuples returned based on tuple density */
double density = baserel->tuples / (double) baserel->pages;
ntuples = npages * density;
}
else
{
/* For lack of data, assume one tuple per page */
ntuples = npages;
}
/* Clamp to the estimated relation size */
ntuples = clamp_row_est(Min(baserel->tuples, ntuples));
*pages = npages;
*tuples = ntuples;
}
/*
* Initialize during executor setup.
*/
static void
system_time_initsamplescan(SampleScanState *node, int eflags)
{
node->tsm_state = palloc0(sizeof(SystemTimeSamplerData));
/* Note the above leaves tsm_state->step equal to zero */
}
/*
* Examine parameters and prepare for a sample scan.
*/
static void
system_time_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed)
{
SystemTimeSamplerData *sampler = (SystemTimeSamplerData *) node->tsm_state;
double millis = DatumGetFloat8(params[0]);
if (millis < 0 || isnan(millis))
ereport(ERROR,
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
errmsg("sample collection time must not be negative")));
sampler->seed = seed;
sampler->millis = millis;
sampler->lt = InvalidOffsetNumber;
sampler->doneblocks = 0;
/* start_time, lb will be initialized during first NextSampleBlock call */
/* we intentionally do not change nblocks/firstblock/step here */
}
/*
* Select next block to sample.
*
* Uses linear probing algorithm for picking next block.
*/
static BlockNumber
system_time_nextsampleblock(SampleScanState *node)
{
SystemTimeSamplerData *sampler = (SystemTimeSamplerData *) node->tsm_state;
HeapScanDesc scan = node->ss.ss_currentScanDesc;
instr_time cur_time;
/* First call within scan? */
if (sampler->doneblocks == 0)
{
/* First scan within query? */
if (sampler->step == 0)
{
/* Initialize now that we have scan descriptor */
SamplerRandomState randstate;
/* If relation is empty, there's nothing to scan */
if (scan->rs_nblocks == 0)
return InvalidBlockNumber;
/* We only need an RNG during this setup step */
sampler_random_init_state(sampler->seed, randstate);
/* Compute nblocks/firstblock/step only once per query */
sampler->nblocks = scan->rs_nblocks;
/* Choose random starting block within the relation */
/* (Actually this is the predecessor of the first block visited) */
sampler->firstblock = sampler_random_fract(randstate) *
sampler->nblocks;
/* Find relative prime as step size for linear probing */
sampler->step = random_relative_prime(sampler->nblocks, randstate);
}
/* Reinitialize lb and start_time */
sampler->lb = sampler->firstblock;
INSTR_TIME_SET_CURRENT(sampler->start_time);
}
/* If we've read all blocks in relation, we're done */
if (++sampler->doneblocks > sampler->nblocks)
return InvalidBlockNumber;
/* If we've used up all the allotted time, we're done */
INSTR_TIME_SET_CURRENT(cur_time);
INSTR_TIME_SUBTRACT(cur_time, sampler->start_time);
if (INSTR_TIME_GET_MILLISEC(cur_time) >= sampler->millis)
return InvalidBlockNumber;
/*
* It's probably impossible for scan->rs_nblocks to decrease between scans
* within a query; but just in case, loop until we select a block number
* less than scan->rs_nblocks. We don't care if scan->rs_nblocks has
* increased since the first scan.
*/
do
{
/* Advance lb, using uint64 arithmetic to forestall overflow */
sampler->lb = ((uint64) sampler->lb + sampler->step) % sampler->nblocks;
} while (sampler->lb >= scan->rs_nblocks);
return sampler->lb;
}
/*
* Select next sampled tuple in current block.
*
* In block sampling, we just want to sample all the tuples in each selected
* block.
*
* When we reach end of the block, return InvalidOffsetNumber which tells
* SampleScan to go to next block.
*/
static OffsetNumber
system_time_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset)
{
SystemTimeSamplerData *sampler = (SystemTimeSamplerData *) node->tsm_state;
OffsetNumber tupoffset = sampler->lt;
/* Advance to next possible offset on page */
if (tupoffset == InvalidOffsetNumber)
tupoffset = FirstOffsetNumber;
else
tupoffset++;
/* Done? */
if (tupoffset > maxoffset)
tupoffset = InvalidOffsetNumber;
sampler->lt = tupoffset;
return tupoffset;
}
/*
* Compute greatest common divisor of two uint32's.
*/
static uint32
gcd(uint32 a, uint32 b)
{
@ -296,22 +330,29 @@ gcd(uint32 a, uint32 b)
return b;
}
/*
* Pick a random value less than and relatively prime to n, if possible
* (else return 1).
*/
static uint32
random_relative_prime(uint32 n, SamplerRandomState randstate)
{
/* Pick random starting number, with some limits on what it can be. */
uint32 r = (uint32) sampler_random_fract(randstate) * n / 2 + n / 4,
t;
uint32 r;
/* Safety check to avoid infinite loop or zero result for small n. */
if (n <= 1)
return 1;
/*
* This should only take 2 or 3 iterations as the probability of 2 numbers
* being relatively prime is ~61%.
* being relatively prime is ~61%; but just in case, we'll include a
* CHECK_FOR_INTERRUPTS in the loop.
*/
while ((t = gcd(r, n)) > 1)
do
{
CHECK_FOR_INTERRUPTS();
r /= t;
}
r = (uint32) (sampler_random_fract(randstate) * n);
} while (r == 0 || gcd(r, n) > 1);
return r;
}

2
contrib/tsm_system_time/tsm_system_time.control
View File

@ -1,5 +1,5 @@
# tsm_system_time extension
comment = 'SYSTEM TABLESAMPLE method which accepts time in milliseconds as a limit'
comment = 'TABLESAMPLE method which accepts time in milliseconds as a limit'
default_version = '1.0'
module_pathname = '$libdir/tsm_system_time'
relocatable = true

120
doc/src/sgml/catalogs.sgml
View File

@ -278,11 +278,6 @@
<entry>planner statistics</entry>
</row>
<row>
<entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
<entry>table sampling methods</entry>
</row>
<row>
<entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
<entry>tablespaces within this database cluster</entry>
@ -6132,121 +6127,6 @@
</sect1>
<sect1 id="catalog-pg-tablesample-method">
<title><structname>pg_tabesample_method</structname></title>
<indexterm zone="catalog-pg-tablesample-method">
<primary>pg_am</primary>
</indexterm>
<para>
The catalog <structname>pg_tablesample_method</structname> stores
information about table sampling methods which can be used in
<command>TABLESAMPLE</command> clause of a <command>SELECT</command>
statement.
</para>
<table>
<title><structname>pg_tablesample_method</> Columns</title>
<tgroup cols="4">
<thead>
<row>
<entry>Name</entry>
<entry>Type</entry>
<entry>References</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><structfield>oid</structfield></entry>
<entry><type>oid</type></entry>
<entry></entry>
<entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
</row>
<row>
<entry><structfield>tsmname</structfield></entry>
<entry><type>name</type></entry>
<entry></entry>
<entry>Name of the sampling method</entry>
</row>
<row>
<entry><structfield>tsmseqscan</structfield></entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>If true, the sampling method scans the whole table sequentially.
</entry>
</row>
<row>
<entry><structfield>tsmpagemode</structfield></entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>If true, the sampling method always reads the pages completely.
</entry>
</row>
<row>
<entry><structfield>tsminit</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry><quote>Initialize the sampling scan</quote> function</entry>
</row>
<row>
<entry><structfield>tsmnextblock</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry><quote>Get next block number</quote> function</entry>
</row>
<row>
<entry><structfield>tsmnexttuple</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry><quote>Get next tuple offset</quote> function</entry>
</row>
<row>
<entry><structfield>tsmexaminetuple</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry>Function which examines the tuple contents and decides if to
return it, or zero if none</entry>
</row>
<row>
<entry><structfield>tsmend</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry><quote>End the sampling scan</quote> function</entry>
</row>
<row>
<entry><structfield>tsmreset</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry><quote>Restart the state of sampling scan</quote> function</entry>
</row>
<row>
<entry><structfield>tsmcost</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry>Costing function</entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>
<sect1 id="catalog-pg-tablespace">
<title><structname>pg_tablespace</structname></title>

11
doc/src/sgml/datatype.sgml
View File

@ -4346,7 +4346,7 @@ SET xmloption TO { DOCUMENT | CONTENT };
an object identifier. There are also several alias types for
<type>oid</>: <type>regproc</>, <type>regprocedure</>,
<type>regoper</>, <type>regoperator</>, <type>regclass</>,
<type>regtype</>, <type>regrole</>, <type>regnamespace</>,
<type>regtype</>, <type>regrole</>, <type>regnamespace</>,
<type>regconfig</>, and <type>regdictionary</>.
<xref linkend="datatype-oid-table"> shows an overview.
</para>
@ -4622,6 +4622,10 @@ SELECT * FROM pg_attribute
<primary>fdw_handler</primary>
</indexterm>
<indexterm zone="datatype-pseudo">
<primary>tsm_handler</primary>
</indexterm>
<indexterm zone="datatype-pseudo">
<primary>cstring</primary>
</indexterm>
@ -4716,6 +4720,11 @@ SELECT * FROM pg_attribute
<entry>A foreign-data wrapper handler is declared to return <type>fdw_handler</>.</entry>
</row>
<row>
<entry><type>tsm_handler</></entry>
<entry>A tablesample method handler is declared to return <type>tsm_handler</>.</entry>
</row>
<row>
<entry><type>record</></entry>
<entry>Identifies a function returning an unspecified row type.</entry>

2
doc/src/sgml/postgres.sgml
View File

@ -243,6 +243,7 @@
&nls;
&plhandler;
&fdwhandler;
&tablesample-method;
&custom-scan;
&geqo;
&indexam;
@ -250,7 +251,6 @@
&spgist;
&gin;
&brin;
&tablesample-method;
&storage;
&bki;
&planstats;

126
doc/src/sgml/ref/select.sgml
View File

@ -49,7 +49,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
<phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
[ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ]
[ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
[ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ]
[ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
<replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
[ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@ -325,50 +326,6 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
</listitem>
</varlistentry>
<varlistentry>
<term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
<listitem>
<para>
Table sample clause after
<replaceable class="parameter">table_name</replaceable> indicates that
a <replaceable class="parameter">sampling_method</replaceable> should
be used to retrieve subset of rows in the table.
The <replaceable class="parameter">sampling_method</replaceable> can be
any sampling method installed in the database. There are currently two
sampling methods available in the standard
<productname>PostgreSQL</productname> distribution:
<itemizedlist>
<listitem>
<para><literal>SYSTEM</literal></para>
</listitem>
<listitem>
<para><literal>BERNOULLI</literal></para>
</listitem>
</itemizedlist>
Both of these sampling methods currently accept only single argument
which is the percent (floating point from 0 to 100) of the rows to
be returned.
The <literal>SYSTEM</literal> sampling method does block level
sampling with each block having the same chance of being selected and
returns all rows from each selected block.
The <literal>BERNOULLI</literal> scans whole table and returns
individual rows with equal probability. Additional sampling methods
may be installed in the database via extensions.
</para>
<para>
The optional parameter <literal>REPEATABLE</literal> uses the seed
parameter, which can be a number or expression producing a number, as
a random seed for sampling. Note that subsequent commands may return
different results even if same <literal>REPEATABLE</literal> clause was
specified. This happens because <acronym>DML</acronym> statements and
maintenance operations such as <command>VACUUM</> may affect physical
distribution of data. The <function>setseed()</> function will not
affect the sampling result when the <literal>REPEATABLE</literal>
parameter is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">alias</replaceable></term>
<listitem>
@ -387,6 +344,61 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
</listitem>
</varlistentry>
<varlistentry>
<term><literal>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</literal></term>
<listitem>
<para>
A <literal>TABLESAMPLE</> clause after
a <replaceable class="parameter">table_name</> indicates that the
specified <replaceable class="parameter">sampling_method</replaceable>
should be used to retrieve a subset of the rows in that table.
This sampling precedes the application of any other filters such
as <literal>WHERE</> clauses.
The standard <productname>PostgreSQL</productname> distribution
includes two sampling methods, <literal>BERNOULLI</literal>
and <literal>SYSTEM</literal>, and other sampling methods can be
installed in the database via extensions.
</para>
<para>
The <literal>BERNOULLI</> and <literal>SYSTEM</> sampling methods
each accept a single <replaceable class="parameter">argument</>
which is the fraction of the table to sample, expressed as a
percentage between 0 and 100. This argument can be
any <type>real</>-valued expression. (Other sampling methods might
accept more or different arguments.) These two methods each return
a randomly-chosen sample of the table that will contain
approximately the specified percentage of the table's rows.
The <literal>BERNOULLI</literal> method scans the whole table and
selects or ignores individual rows independently with the specified
probability.
The <literal>SYSTEM</literal> method does block-level sampling with
each block having the specified chance of being selected; all rows
in each selected block are returned.
The <literal>SYSTEM</literal> method is significantly faster than
the <literal>BERNOULLI</literal> method when small sampling
percentages are specified, but it may return a less-random sample of
the table as a result of clustering effects.
</para>
<para>
The optional <literal>REPEATABLE</literal> clause specifies
a <replaceable class="parameter">seed</> number or expression to use
for generating random numbers within the sampling method. The seed
value can be any non-null floating-point value. Two queries that
specify the same seed and <replaceable class="parameter">argument</>
values will select the same sample of the table, if the table has
not been changed meanwhile. But different seed values will usually
produce different samples.
If <literal>REPEATABLE</literal> is not given then a new random
sample is selected for each query.
Note that some add-on sampling methods do not
accept <literal>REPEATABLE</literal>, and will always produce new
samples on each use.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">select</replaceable></term>
<listitem>
@ -1870,6 +1882,16 @@ SELECT distributors.* WHERE distributors.name = 'Westward';
</para>
</refsect2>
<refsect2>
<title><literal>TABLESAMPLE</literal> Clause Restrictions</title>
<para>
The <literal>TABLESAMPLE</> clause is currently accepted only on
regular tables and materialized views. According to the SQL standard
it should be possible to apply it to any <literal>FROM</> item.
</para>
</refsect2>
<refsect2>
<title>Function Calls in <literal>FROM</literal></title>
@ -1993,19 +2015,5 @@ SELECT distributors.* WHERE distributors.name = 'Westward';
</para>
</refsect2>
<refsect2>
<title><literal>TABLESAMPLE</literal> clause</title>
<para>
The <literal>TABLESAMPLE</> clause is currently accepted only on physical
relations and materialized views.
</para>
<para>
Additional modules allow you to install custom sampling methods and use
them instead of the SQL standard methods.
</para>
</refsect2>
</refsect1>
</refentry>

346
doc/src/sgml/tablesample-method.sgml
View File

@ -1,139 +1,301 @@
<!-- doc/src/sgml/tablesample-method.sgml -->
<chapter id="tablesample-method">
<title>Writing A TABLESAMPLE Sampling Method</title>
<title>Writing A Table Sampling Method</title>
<indexterm zone="tablesample-method">
<primary>tablesample method</primary>
<primary>table sampling method</primary>
</indexterm>
<indexterm zone="tablesample-method">
<primary><literal>TABLESAMPLE</literal> method</primary>
</indexterm>
<para>
The <command>TABLESAMPLE</command> clause implementation in
<productname>PostgreSQL</> supports creating a custom sampling methods.
These methods control what sample of the table will be returned when the
<command>TABLESAMPLE</command> clause is used.
<productname>PostgreSQL</>'s implementation of the <literal>TABLESAMPLE</>
clause supports custom table sampling methods, in addition to
the <literal>BERNOULLI</> and <literal>SYSTEM</> methods that are required
by the SQL standard. The sampling method determines which rows of the
table will be selected when the <literal>TABLESAMPLE</> clause is used.
</para>
<sect1 id="tablesample-method-functions">
<title>Tablesample Method Functions</title>
<para>
At the SQL level, a table sampling method is represented by a single SQL
function, typically implemented in C, having the signature
<programlisting>
method_name(internal) RETURNS tsm_handler
</programlisting>
The name of the function is the same method name appearing in the
<literal>TABLESAMPLE</> clause. The <type>internal</> argument is a dummy
(always having value zero) that simply serves to prevent this function from
being called directly from a SQL command.
The result of the function must be a palloc'd struct of
type <type>TsmRoutine</>, which contains pointers to support functions for
the sampling method. These support functions are plain C functions and
are not visible or callable at the SQL level. The support functions are
described in <xref linkend="tablesample-support-functions">.
</para>
<para>
In addition to function pointers, the <type>TsmRoutine</> struct must
provide these additional fields:
</para>
<variablelist>
<varlistentry>
<term><literal>List *parameterTypes</literal></term>
<listitem>
<para>
This is an OID list containing the data type OIDs of the parameter(s)
that will be accepted by the <literal>TABLESAMPLE</> clause when this
sampling method is used. For example, for the built-in methods, this
list contains a single item with value <literal>FLOAT4OID</>, which
represents the sampling percentage. Custom sampling methods can have
more or different parameters.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>bool repeatable_across_queries</literal></term>
<listitem>
<para>
If <literal>true</>, the sampling method can deliver identical samples
across successive queries, if the same parameters
and <literal>REPEATABLE</> seed value are supplied each time and the
table contents have not changed. When this is <literal>false</>,
the <literal>REPEATABLE</> clause is not accepted for use with the
sampling method.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>bool repeatable_across_scans</literal></term>
<listitem>
<para>
If <literal>true</>, the sampling method can deliver identical samples
across successive scans in the same query (assuming unchanging
parameters, seed value, and snapshot).
When this is <literal>false</>, the planner will not select plans that
would require scanning the sampled table more than once, since that
might result in inconsistent query output.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
The <type>TsmRoutine</> struct type is declared
in <filename>src/include/access/tsmapi.h</>, which see for additional
details.
</para>
<para>
The table sampling methods included in the standard distribution are good
references when trying to write your own. Look into
the <filename>src/backend/access/tablesample</> subdirectory of the source
tree for the built-in sampling methods, and into the <filename>contrib</>
subdirectory for add-on methods.
</para>
<sect1 id="tablesample-support-functions">
<title>Sampling Method Support Functions</title>
<para>
The tablesample method must provide following set of functions:
The TSM handler function returns a palloc'd <type>TsmRoutine</> struct
containing pointers to the support functions described below. Most of
the functions are required, but some are optional, and those pointers can
be NULL.
</para>
<para>
<programlisting>
void
tsm_init (TableSampleDesc *desc,
uint32 seed, ...);
SampleScanGetSampleSize (PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
</programlisting>
Initialize the tablesample scan. The function is called at the beginning
of each relation scan.
This function is called during planning. It must estimate the number of
relation pages that will be read during a sample scan, and the number of
tuples that will be selected by the scan. (For example, these might be
determined by estimating the sampling fraction, and then multiplying
the <literal>baserel-&gt;pages</> and <literal>baserel-&gt;tuples</>
numbers by that, being sure to round the results to integral values.)
The <literal>paramexprs</> list holds the expression(s) that are
parameters to the <literal>TABLESAMPLE</> clause. It is recommended to
use <function>estimate_expression_value()</> to try to reduce these
expressions to constants, if their values are needed for estimation
purposes; but the function must provide size estimates even if they cannot
be reduced, and it should not fail even if the values appear invalid
(remember that they're only estimates of what the run-time values will be).
The <literal>pages</> and <literal>tuples</> parameters are outputs.
</para>
<para>
Note that the first two parameters are required but you can specify
additional parameters which then will be used by the <command>TABLESAMPLE</>
clause to determine the required user input in the query itself.
This means that if your function will specify additional float4 parameter
named percent, the user will have to call the tablesample method with
expression which evaluates (or can be coerced) to float4.
For example this definition:
<programlisting>
tsm_init (TableSampleDesc *desc,
uint32 seed, float4 pct);
void
InitSampleScan (SampleScanState *node,
int eflags);
</programlisting>
Will lead to SQL call like this:
Initialize for execution of a SampleScan plan node.
This is called during executor startup.
It should perform any initialization needed before processing can start.
The <structname>SampleScanState</> node has already been created, but
its <structfield>tsm_state</> field is NULL.
The <function>InitSampleScan</> function can palloc whatever internal
state data is needed by the sampling method, and store a pointer to
it in <literal>node-&gt;tsm_state</>.
Information about the table to scan is accessible through other fields
of the <structname>SampleScanState</> node (but note that the
<literal>node-&gt;ss.ss_currentScanDesc</> scan descriptor is not set
up yet).
<literal>eflags</> contains flag bits describing the executor's
operating mode for this plan node.
</para>
<para>
When <literal>(eflags &amp; EXEC_FLAG_EXPLAIN_ONLY)</> is true,
the scan will not actually be performed, so this function should only do
the minimum required to make the node state valid for <command>EXPLAIN</>
and <function>EndSampleScan</>.
</para>
<para>
This function can be omitted (set the pointer to NULL), in which case
<function>BeginSampleScan</> must perform all initialization needed
by the sampling method.
</para>
<para>
<programlisting>
... TABLESAMPLE yourmethod(0.5) ...
void
BeginSampleScan (SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
</programlisting>
Begin execution of a sampling scan.
This is called just before the first attempt to fetch a tuple, and
may be called again if the scan needs to be restarted.
Information about the table to scan is accessible through fields
of the <structname>SampleScanState</> node (but note that the
<literal>node-&gt;ss.ss_currentScanDesc</> scan descriptor is not set
up yet).
The <literal>params</> array, of length <literal>nparams</>, contains the
values of the parameters supplied in the <literal>TABLESAMPLE</> clause.
These will have the number and types specified in the sampling
method's <literal>parameterTypes</literal> list, and have been checked
to not be null.
<literal>seed</> contains a seed to use for any random numbers generated
within the sampling method; it is either a hash derived from the
<literal>REPEATABLE</> value if one was given, or the result
of <literal>random()</> if not.
</para>
<para>
This function may adjust the fields <literal>node-&gt;use_bulkread</>
and <literal>node-&gt;use_pagemode</>.
If <literal>node-&gt;use_bulkread</> is <literal>true</>, which it is by
default, the scan will use a buffer access strategy that encourages
recycling buffers after use. It might be reasonable to set this
to <literal>false</> if the scan will visit only a small fraction of the
table's pages.
If <literal>node-&gt;use_pagemode</> is <literal>true</>, which it is by
default, the scan will perform visibility checking in a single pass for
all tuples on each visited page. It might be reasonable to set this
to <literal>false</> if the scan will select only a small fraction of the
tuples on each visited page. That will result in fewer tuple visibility
checks being performed, though each one will be more expensive because it
will require more locking.
</para>
<para>
If the sampling method is
marked <literal>repeatable_across_scans</literal>, it must be able to
select the same set of tuples during a rescan as it did originally, that is
a fresh call of <function>BeginSampleScan</> must lead to selecting the
same tuples as before (if the <literal>TABLESAMPLE</> parameters
and seed don't change).
</para>
<para>
<programlisting>
BlockNumber
tsm_nextblock (TableSampleDesc *desc);
NextSampleBlock (SampleScanState *node);
</programlisting>
Returns the block number of next page to be scanned. InvalidBlockNumber
should be returned if the sampling has reached end of the relation.
Returns the block number of the next page to be scanned, or
<literal>InvalidBlockNumber</> if no pages remain to be scanned.
</para>
<para>
This function can be omitted (set the pointer to NULL), in which case
the core code will perform a sequential scan of the entire relation.
Such a scan can use synchronized scanning, so that the sampling method
cannot assume that the relation pages are visited in the same order on
each scan.
</para>
<para>
<programlisting>
OffsetNumber
tsm_nexttuple (TableSampleDesc *desc, BlockNumber blockno,
OffsetNumber maxoffset);
NextSampleTuple (SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
</programlisting>
Return next tuple offset for the current page. InvalidOffsetNumber should
be returned if the sampling has reached end of the page.
Returns the offset number of the next tuple to be sampled on the
specified page, or <literal>InvalidOffsetNumber</> if no tuples remain to
be sampled. <literal>maxoffset</> is the largest offset number in use
on the page.
</para>
<note>
<para>
<function>NextSampleTuple</> is not explicitly told which of the offset
numbers in the range <literal>1 .. maxoffset</> actually contain valid
tuples. This is not normally a problem since the core code ignores
requests to sample missing or invisible tuples; that should not result in
any bias in the sample. However, if necessary, the function can
examine <literal>node-&gt;ss.ss_currentScanDesc-&gt;rs_vistuples[]</>
to identify which tuples are valid and visible. (This
requires <literal>node-&gt;use_pagemode</> to be <literal>true</>.)
</para>
</note>
<note>
<para>
<function>NextSampleTuple</> must <emphasis>not</> assume
that <literal>blockno</> is the same page number returned by the most
recent <function>NextSampleBlock</> call. It was returned by some
previous <function>NextSampleBlock</> call, but the core code is allowed
to call <function>NextSampleBlock</> in advance of actually scanning
pages, so as to support prefetching. It is OK to assume that once
sampling of a given page begins, successive <function>NextSampleTuple</>
calls all refer to the same page until <literal>InvalidOffsetNumber</> is
returned.
</para>
</note>
<para>
<programlisting>
void
tsm_end (TableSampleDesc *desc);
EndSampleScan (SampleScanState *node);
</programlisting>
The scan has finished, cleanup any left over state.
End the scan and release resources. It is normally not important
to release palloc'd memory, but any externally-visible resources
should be cleaned up.
This function can be omitted (set the pointer to NULL) in the common
case where no such resources exist.
</para>
<para>
<programlisting>
void
tsm_reset (TableSampleDesc *desc);
</programlisting>
The scan needs to rescan the relation again, reset any tablesample method
state.
</para>
<para>
<programlisting>
void
tsm_cost (PlannerInfo *root, Path *path, RelOptInfo *baserel,
List *args, BlockNumber *pages, double *tuples);
</programlisting>
This function is used by optimizer to decide best plan and is also used
for output of <command>EXPLAIN</>.
</para>
<para>
There is one more function which tablesampling method can implement in order
to gain more fine grained control over sampling. This function is optional:
</para>
<para>
<programlisting>
bool
tsm_examinetuple (TableSampleDesc *desc, BlockNumber blockno,
HeapTuple tuple, bool visible);
</programlisting>
Function that enables the sampling method to examine contents of the tuple
(for example to collect some internal statistics). The return value of this
function is used to determine if the tuple should be returned to client.
Note that this function will receive even invisible tuples but it is not
allowed to return true for such tuple (if it does,
<productname>PostgreSQL</> will raise an error).
</para>
<para>
As you can see most of the tablesample method interfaces get the
<structname>TableSampleDesc</> as a first parameter. This structure holds
state of the current scan and also provides storage for the tablesample
method's state. It is defined as following:
<programlisting>
typedef struct TableSampleDesc {
HeapScanDesc heapScan;
TupleDesc tupDesc;
void *tsmdata;
} TableSampleDesc;
</programlisting>
Where <structfield>heapScan</> is the descriptor of the physical table scan.
It's possible to get table size info from it. The <structfield>tupDesc</>
represents the tuple descriptor of the tuples returned by the scan and passed
to the <function>tsm_examinetuple()</> interface. The <structfield>tsmdata</>
can be used by tablesample method itself to store any state info it might
need during the scan. If used by the method, it should be <function>pfree</>d
in <function>tsm_end()</> function.
</para>
</sect1>
</chapter>

39
doc/src/sgml/tsm-system-rows.sgml
View File

@ -8,24 +8,37 @@
</indexterm>
<para>
The <filename>tsm_system_rows</> module provides the tablesample method
<literal>SYSTEM_ROWS</literal>, which can be used inside the
<command>TABLESAMPLE</command> clause of a <command>SELECT</command>.
The <filename>tsm_system_rows</> module provides the table sampling method
<literal>SYSTEM_ROWS</literal>, which can be used in
the <literal>TABLESAMPLE</> clause of a <xref linkend="sql-select">
command.
</para>
<para>
This tablesample method uses a linear probing algorithm to read sample
of a table and uses actual number of rows as limit (unlike the
<literal>SYSTEM</literal> tablesample method which limits by percentage
of a table).
This table sampling method accepts a single integer argument that is the
maximum number of rows to read. The resulting sample will always contain
exactly that many rows, unless the table does not contain enough rows, in
which case the whole table is selected.
</para>
<para>
Like the built-in <literal>SYSTEM</literal> sampling
method, <literal>SYSTEM_ROWS</literal> performs block-level sampling, so
that the sample is not completely random but may be subject to clustering
effects, especially if only a small number of rows are requested.
</para>
<para>
<literal>SYSTEM_ROWS</literal> does not support
the <literal>REPEATABLE</literal> clause.
</para>
<sect2>
<title>Examples</title>
<para>
Here is an example of selecting sample of a table with
<literal>SYSTEM_ROWS</>. First install the extension:
Here is an example of selecting a sample of a table with
<literal>SYSTEM_ROWS</>. First install the extension:
</para>
<programlisting>
@ -33,8 +46,7 @@ CREATE EXTENSION tsm_system_rows;
</programlisting>
<para>
Then you can use it in <command>SELECT</command> command same way as other
tablesample methods:
Then you can use it in a <command>SELECT</command> command, for instance:
<programlisting>
SELECT * FROM my_table TABLESAMPLE SYSTEM_ROWS(100);
@ -42,8 +54,9 @@ SELECT * FROM my_table TABLESAMPLE SYSTEM_ROWS(100);
</para>
<para>
The above command will return a sample of 100 rows from the table my_table
(less if the table does not have 100 visible rows).
This command will return a sample of 100 rows from the
table <structname>my_table</> (unless the table does not have 100
visible rows, in which case all its rows are returned).
</para>
</sect2>

42
doc/src/sgml/tsm-system-time.sgml
View File

@ -8,25 +8,39 @@
</indexterm>
<para>
The <filename>tsm_system_time</> module provides the tablesample method
<literal>SYSTEM_TIME</literal>, which can be used inside the
<command>TABLESAMPLE</command> clause of a <command>SELECT</command>.
The <filename>tsm_system_time</> module provides the table sampling method
<literal>SYSTEM_TIME</literal>, which can be used in
the <literal>TABLESAMPLE</> clause of a <xref linkend="sql-select">
command.
</para>
<para>
This tablesample method uses a linear probing algorithm to read sample
of a table and uses time in milliseconds as limit (unlike the
<literal>SYSTEM</literal> tablesample method which limits by percentage
of a table). This gives you some control over the length of execution
of your query.
This table sampling method accepts a single floating-point argument that
is the maximum number of milliseconds to spend reading the table. This
gives you direct control over how long the query takes, at the price that
the size of the sample becomes hard to predict. The resulting sample will
contain as many rows as could be read in the specified time, unless the
whole table has been read first.
</para>
<para>
Like the built-in <literal>SYSTEM</literal> sampling
method, <literal>SYSTEM_TIME</literal> performs block-level sampling, so
that the sample is not completely random but may be subject to clustering
effects, especially if only a small number of rows are selected.
</para>
<para>
<literal>SYSTEM_TIME</literal> does not support
the <literal>REPEATABLE</literal> clause.
</para>
<sect2>
<title>Examples</title>
<para>
Here is an example of selecting sample of a table with
<literal>SYSTEM_TIME</>. First install the extension:
Here is an example of selecting a sample of a table with
<literal>SYSTEM_TIME</>. First install the extension:
</para>
<programlisting>
@ -34,8 +48,7 @@ CREATE EXTENSION tsm_system_time;
</programlisting>
<para>
Then you can use it in a <command>SELECT</command> command the same way as
other tablesample methods:
Then you can use it in a <command>SELECT</command> command, for instance:
<programlisting>
SELECT * FROM my_table TABLESAMPLE SYSTEM_TIME(1000);
@ -43,8 +56,9 @@ SELECT * FROM my_table TABLESAMPLE SYSTEM_TIME(1000);
</para>
<para>
The above command will return as large a sample of my_table as it can read in
1 second (or less if it reads whole table faster).
This command will return as large a sample of <structname>my_table</> as
it can read in 1 second (1000 milliseconds). Of course, if the whole
table can be read in under 1 second, all its rows will be returned.
</para>
</sect2>

61
src/backend/access/heap/heapam.c
View File

@ -80,8 +80,11 @@ bool synchronize_seqscans = true;
static HeapScanDesc heap_beginscan_internal(Relation relation,
Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode,
bool is_bitmapscan, bool is_samplescan,
bool allow_strat,
bool allow_sync,
bool allow_pagemode,
bool is_bitmapscan,
bool is_samplescan,
bool temp_snap);
static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
TransactionId xid, CommandId cid, int options);
@ -207,7 +210,7 @@ static const int MultiXactStatusLock[MaxMultiXactStatus + 1] =
* ----------------
*/
static void
initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
initscan(HeapScanDesc scan, ScanKey key, bool keep_startblock)
{
bool allow_strat;
bool allow_sync;
@ -257,12 +260,12 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
scan->rs_strategy = NULL;
}
if (is_rescan)
if (keep_startblock)
{
/*
* If rescan, keep the previous startblock setting so that rewinding a
* cursor doesn't generate surprising results. Reset the syncscan
* setting, though.
* When rescanning, we want to keep the previous startblock setting,
* so that rewinding a cursor doesn't generate surprising results.
* Reset the active syncscan setting, though.
*/
scan->rs_syncscan = (allow_sync && synchronize_seqscans);
}
@ -1313,6 +1316,10 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
/* ----------------
* heap_beginscan - begin relation scan
*
* heap_beginscan is the "standard" case.
*
* heap_beginscan_catalog differs in setting up its own temporary snapshot.
*
* heap_beginscan_strat offers an extended API that lets the caller control
* whether a nondefault buffer access strategy can be used, and whether
* syncscan can be chosen (possibly resulting in the scan not starting from
@ -1323,8 +1330,11 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
* really quite unlike a standard seqscan, there is just enough commonality
* to make it worth using the same data structure.
*
* heap_beginscan_samplingscan is alternate entry point for setting up a
* HeapScanDesc for a TABLESAMPLE scan.
* heap_beginscan_sampling is an alternative entry point for setting up a
* HeapScanDesc for a TABLESAMPLE scan. As with bitmap scans, it's worth
* using the same data structure although the behavior is rather different.
* In addition to the options offered by heap_beginscan_strat, this call
* also allows control of whether page-mode visibility checking is used.
* ----------------
*/
HeapScanDesc
@ -1366,18 +1376,22 @@ heap_beginscan_bm(Relation relation, Snapshot snapshot,
HeapScanDesc
heap_beginscan_sampling(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_pagemode)
bool allow_strat, bool allow_sync, bool allow_pagemode)
{
return heap_beginscan_internal(relation, snapshot, nkeys, key,
allow_strat, false, allow_pagemode,
allow_strat, allow_sync, allow_pagemode,
false, true, false);
}
static HeapScanDesc
heap_beginscan_internal(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode,
bool is_bitmapscan, bool is_samplescan, bool temp_snap)
bool allow_strat,
bool allow_sync,
bool allow_pagemode,
bool is_bitmapscan,
bool is_samplescan,
bool temp_snap)
{
HeapScanDesc scan;
@ -1461,6 +1475,27 @@ heap_rescan(HeapScanDesc scan,
initscan(scan, key, true);
}
/* ----------------
* heap_rescan_set_params - restart a relation scan after changing params
*
* This call allows changing the buffer strategy, syncscan, and pagemode
* options before starting a fresh scan. Note that although the actual use
* of syncscan might change (effectively, enabling or disabling reporting),
* the previously selected startblock will be kept.
* ----------------
*/
void
heap_rescan_set_params(HeapScanDesc scan, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode)
{
/* adjust parameters */
scan->rs_allow_strat = allow_strat;
scan->rs_allow_sync = allow_sync;
scan->rs_pageatatime = allow_pagemode && IsMVCCSnapshot(scan->rs_snapshot);
/* ... and rescan */
heap_rescan(scan, key);
}
/* ----------------
* heap_endscan - end relation scan
*

6
src/backend/access/tablesample/Makefile
View File

@ -1,10 +1,10 @@
#-------------------------------------------------------------------------
#
# Makefile--
# Makefile for utils/tablesample
# Makefile for access/tablesample
#
# IDENTIFICATION
# src/backend/utils/tablesample/Makefile
# src/backend/access/tablesample/Makefile
#
#-------------------------------------------------------------------------
@ -12,6 +12,6 @@ subdir = src/backend/access/tablesample
top_builddir = ../../../..
include $(top_builddir)/src/Makefile.global
OBJS = tablesample.o system.o bernoulli.o
OBJS = bernoulli.o system.o tablesample.o
include $(top_srcdir)/src/backend/common.mk

332
src/backend/access/tablesample/bernoulli.c
View File

@ -1,233 +1,231 @@
/*-------------------------------------------------------------------------
*
* bernoulli.c
* interface routines for BERNOULLI tablesample method
* support routines for BERNOULLI tablesample method
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* To ensure repeatability of samples, it is necessary that selection of a
* given tuple be history-independent; otherwise syncscanning would break
* repeatability, to say nothing of logically-irrelevant maintenance such
* as physical extension or shortening of the relation.
*
* To achieve that, we proceed by hashing each candidate TID together with
* the active seed, and then selecting it if the hash is less than the
* cutoff value computed from the selection probability by BeginSampleScan.
*
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/utils/tablesample/bernoulli.c
* src/backend/access/tablesample/bernoulli.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "fmgr.h"
#ifdef _MSC_VER
#include <float.h> /* for _isnan */
#endif
#include <math.h>
#include "access/tablesample.h"
#include "access/relscan.h"
#include "nodes/execnodes.h"
#include "nodes/relation.h"
#include "access/hash.h"
#include "access/tsmapi.h"
#include "catalog/pg_type.h"
#include "optimizer/clauses.h"
#include "storage/bufmgr.h"
#include "utils/sampling.h"
#include "optimizer/cost.h"
#include "utils/builtins.h"
/* tsdesc */
/* Private state */
typedef struct
{
uint64 cutoff; /* select tuples with hash less than this */
uint32 seed; /* random seed */
BlockNumber startblock; /* starting block, we use ths for syncscan
* support */
BlockNumber nblocks; /* number of blocks */
BlockNumber blockno; /* current block */
float4 probability; /* probabilty that tuple will be returned
* (0.0-1.0) */
OffsetNumber lt; /* last tuple returned from current block */
SamplerRandomState randstate; /* random generator tsdesc */
} BernoulliSamplerData;
static void bernoulli_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
static void bernoulli_initsamplescan(SampleScanState *node,
int eflags);
static void bernoulli_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
static OffsetNumber bernoulli_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
/*
* Initialize the state.
* Create a TsmRoutine descriptor for the BERNOULLI method.
*/
Datum
tsm_bernoulli_init(PG_FUNCTION_ARGS)
tsm_bernoulli_handler(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
uint32 seed = PG_GETARG_UINT32(1);
float4 percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
HeapScanDesc scan = tsdesc->heapScan;
BernoulliSamplerData *sampler;
TsmRoutine *tsm = makeNode(TsmRoutine);
if (percent < 0 || percent > 100)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("invalid sample size"),
errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
tsm->parameterTypes = list_make1_oid(FLOAT4OID);
tsm->repeatable_across_queries = true;
tsm->repeatable_across_scans = true;
tsm->SampleScanGetSampleSize = bernoulli_samplescangetsamplesize;
tsm->InitSampleScan = bernoulli_initsamplescan;
tsm->BeginSampleScan = bernoulli_beginsamplescan;
tsm->NextSampleBlock = NULL;
tsm->NextSampleTuple = bernoulli_nextsampletuple;
tsm->EndSampleScan = NULL;
sampler = palloc0(sizeof(BernoulliSamplerData));
/* Remember initial values for reinit */
sampler->seed = seed;
sampler->startblock = scan->rs_startblock;
sampler->nblocks = scan->rs_nblocks;
sampler->blockno = InvalidBlockNumber;
sampler->probability = percent / 100;
sampler->lt = InvalidOffsetNumber;
sampler_random_init_state(sampler->seed, sampler->randstate);
tsdesc->tsmdata = (void *) sampler;
PG_RETURN_VOID();
PG_RETURN_POINTER(tsm);
}
/*
* Get next block number to read or InvalidBlockNumber if we are at the
* end of the relation.
* Sample size estimation.
*/
Datum
tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
static void
bernoulli_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
BernoulliSamplerData *sampler = (BernoulliSamplerData *) tsdesc->tsmdata;
Node *pctnode;
float4 samplefract;
/*
* Bernoulli sampling scans all blocks on the table and supports syncscan
* so loop from startblock to startblock instead of from 0 to nblocks.
*/
if (sampler->blockno == InvalidBlockNumber)
sampler->blockno = sampler->startblock;
/* Try to extract an estimate for the sample percentage */
pctnode = (Node *) linitial(paramexprs);
pctnode = estimate_expression_value(root, pctnode);
if (IsA(pctnode, Const) &&
!((Const *) pctnode)->constisnull)
{
samplefract = DatumGetFloat4(((Const *) pctnode)->constvalue);
if (samplefract >= 0 && samplefract <= 100 && !isnan(samplefract))
samplefract /= 100.0f;
else
{
/* Default samplefract if the value is bogus */
samplefract = 0.1f;
}
}
else
{
sampler->blockno++;
if (sampler->blockno >= sampler->nblocks)
sampler->blockno = 0;
if (sampler->blockno == sampler->startblock)
PG_RETURN_UINT32(InvalidBlockNumber);
/* Default samplefract if we didn't obtain a non-null Const */
samplefract = 0.1f;
}
PG_RETURN_UINT32(sampler->blockno);
/* We'll visit all pages of the baserel */
*pages = baserel->pages;
*tuples = clamp_row_est(baserel->tuples * samplefract);
}
/*
* Get next tuple from current block.
* Initialize during executor setup.
*/
static void
bernoulli_initsamplescan(SampleScanState *node, int eflags)
{
node->tsm_state = palloc0(sizeof(BernoulliSamplerData));
}
/*
* Examine parameters and prepare for a sample scan.
*/
static void
bernoulli_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed)
{
BernoulliSamplerData *sampler = (BernoulliSamplerData *) node->tsm_state;
double percent = DatumGetFloat4(params[0]);
if (percent < 0 || percent > 100 || isnan(percent))
ereport(ERROR,
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
errmsg("sample percentage must be between 0 and 100")));
/*
* The cutoff is sample probability times (PG_UINT32_MAX + 1); we have to
* store that as a uint64, of course. Note that this gives strictly
* correct behavior at the limits of zero or one probability.
*/
sampler->cutoff = rint(((double) PG_UINT32_MAX + 1) * percent / 100);
sampler->seed = seed;
sampler->lt = InvalidOffsetNumber;
/*
* Use bulkread, since we're scanning all pages. But pagemode visibility
* checking is a win only at larger sampling fractions. The 25% cutoff
* here is based on very limited experimentation.
*/
node->use_bulkread = true;
node->use_pagemode = (percent >= 25);
}
/*
* Select next sampled tuple in current block.
*
* This method implements the main logic in bernoulli sampling.
* The algorithm simply generates new random number (in 0.0-1.0 range) and if
* it falls within user specified probability (in the same range) return the
* tuple offset.
* It is OK here to return an offset without knowing if the tuple is visible
* (or even exists). The reason is that we do the coinflip for every tuple
* offset in the table. Since all tuples have the same probability of being
* returned, it doesn't matter if we do extra coinflips for invisible tuples.
*
* It is ok here to return tuple offset without knowing if tuple is visible
* and not check it via examinetuple. The reason for that is that we do the
* coinflip (random number generation) for every tuple in the table. Since all
* tuples have same probability of being returned the visible and invisible
* tuples will be returned in same ratio as they have in the actual table.
* This means that there is no skew towards either visible or invisible tuples
* and the number of visible tuples returned from the executor node should
* match the fraction of visible tuples which was specified by user.
*
* This is faster than doing the coinflip in examinetuple because we don't
* have to do visibility checks on uninteresting tuples.
*
* If we reach end of the block return InvalidOffsetNumber which tells
* When we reach end of the block, return InvalidOffsetNumber which tells
* SampleScan to go to next block.
*/
Datum
tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
static OffsetNumber
bernoulli_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
OffsetNumber maxoffset = PG_GETARG_UINT16(2);
BernoulliSamplerData *sampler = (BernoulliSamplerData *) tsdesc->tsmdata;
BernoulliSamplerData *sampler = (BernoulliSamplerData *) node->tsm_state;
OffsetNumber tupoffset = sampler->lt;
float4 probability = sampler->probability;
uint32 hashinput[3];
/* Advance to first/next tuple in block */
if (tupoffset == InvalidOffsetNumber)
tupoffset = FirstOffsetNumber;
else
tupoffset++;
/*
* Loop over tuple offsets until the random generator returns value that
* is within the probability of returning the tuple or until we reach end
* of the block.
* We compute the hash by applying hash_any to an array of 3 uint32's
* containing the block, offset, and seed. This is efficient to set up,
* and with the current implementation of hash_any, it gives
* machine-independent results, which is a nice property for regression
* testing.
*
* (This is our implementation of bernoulli trial)
* These words in the hash input are the same throughout the block:
*/
while (sampler_random_fract(sampler->randstate) > probability)
{
tupoffset++;
hashinput[0] = blockno;
hashinput[2] = sampler->seed;
if (tupoffset > maxoffset)
/*
* Loop over tuple offsets until finding suitable TID or reaching end of
* block.
*/
for (; tupoffset <= maxoffset; tupoffset++)
{
uint32 hash;
hashinput[1] = tupoffset;
hash = DatumGetUInt32(hash_any((const unsigned char *) hashinput,
(int) sizeof(hashinput)));
if (hash < sampler->cutoff)
break;
}
if (tupoffset > maxoffset)
/* Tell SampleScan that we want next block. */
tupoffset = InvalidOffsetNumber;
sampler->lt = tupoffset;
PG_RETURN_UINT16(tupoffset);
}
/*
* Cleanup method.
*/
Datum
tsm_bernoulli_end(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
pfree(tsdesc->tsmdata);
PG_RETURN_VOID();
}
/*
* Reset tsdesc (called by ReScan).
*/
Datum
tsm_bernoulli_reset(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
BernoulliSamplerData *sampler = (BernoulliSamplerData *) tsdesc->tsmdata;
sampler->blockno = InvalidBlockNumber;
sampler->lt = InvalidOffsetNumber;
sampler_random_init_state(sampler->seed, sampler->randstate);
PG_RETURN_VOID();
}
/*
* Costing function.
*/
Datum
tsm_bernoulli_cost(PG_FUNCTION_ARGS)
{
PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
Path *path = (Path *) PG_GETARG_POINTER(1);
RelOptInfo *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
List *args = (List *) PG_GETARG_POINTER(3);
BlockNumber *pages = (BlockNumber *) PG_GETARG_POINTER(4);
double *tuples = (double *) PG_GETARG_POINTER(5);
Node *pctnode;
float4 samplesize;
*pages = baserel->pages;
pctnode = linitial(args);
pctnode = estimate_expression_value(root, pctnode);
if (IsA(pctnode, RelabelType))
pctnode = (Node *) ((RelabelType *) pctnode)->arg;
if (IsA(pctnode, Const))
{
samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
samplesize /= 100.0;
}
else
{
/* Default samplesize if the estimation didn't return Const. */
samplesize = 0.1f;
}
*tuples = path->rows * samplesize;
path->rows = *tuples;
PG_RETURN_VOID();
return tupoffset;
}

338
src/backend/access/tablesample/system.c
View File

@ -1,186 +1,260 @@
/*-------------------------------------------------------------------------
*
* system.c
* interface routines for system tablesample method
* support routines for SYSTEM tablesample method
*
* To ensure repeatability of samples, it is necessary that selection of a
* given tuple be history-independent; otherwise syncscanning would break
* repeatability, to say nothing of logically-irrelevant maintenance such
* as physical extension or shortening of the relation.
*
* To achieve that, we proceed by hashing each candidate block number together
* with the active seed, and then selecting it if the hash is less than the
* cutoff value computed from the selection probability by BeginSampleScan.
*
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/utils/tablesample/system.c
* src/backend/access/tablesample/system.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "fmgr.h"
#ifdef _MSC_VER
#include <float.h> /* for _isnan */
#endif
#include <math.h>
#include "access/tablesample.h"
#include "access/hash.h"
#include "access/relscan.h"
#include "nodes/execnodes.h"
#include "nodes/relation.h"
#include "access/tsmapi.h"
#include "catalog/pg_type.h"
#include "optimizer/clauses.h"
#include "storage/bufmgr.h"
#include "utils/sampling.h"
#include "optimizer/cost.h"
#include "utils/builtins.h"
/*
* State
*/
/* Private state */
typedef struct
{
BlockSamplerData bs;
uint64 cutoff; /* select blocks with hash less than this */
uint32 seed; /* random seed */
BlockNumber nblocks; /* number of block in relation */
int samplesize; /* number of blocks to return */
BlockNumber nextblock; /* next block to consider sampling */
OffsetNumber lt; /* last tuple returned from current block */
} SystemSamplerData;
static void system_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
static void system_initsamplescan(SampleScanState *node,
int eflags);
static void system_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
static BlockNumber system_nextsampleblock(SampleScanState *node);
static OffsetNumber system_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
/*
* Initializes the state.
* Create a TsmRoutine descriptor for the SYSTEM method.
*/
Datum
tsm_system_init(PG_FUNCTION_ARGS)
tsm_system_handler(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
uint32 seed = PG_GETARG_UINT32(1);
float4 percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
HeapScanDesc scan = tsdesc->heapScan;
SystemSamplerData *sampler;
TsmRoutine *tsm = makeNode(TsmRoutine);
if (percent < 0 || percent > 100)
tsm->parameterTypes = list_make1_oid(FLOAT4OID);
tsm->repeatable_across_queries = true;
tsm->repeatable_across_scans = true;
tsm->SampleScanGetSampleSize = system_samplescangetsamplesize;
tsm->InitSampleScan = system_initsamplescan;
tsm->BeginSampleScan = system_beginsamplescan;
tsm->NextSampleBlock = system_nextsampleblock;
tsm->NextSampleTuple = system_nextsampletuple;
tsm->EndSampleScan = NULL;
PG_RETURN_POINTER(tsm);
}
/*
* Sample size estimation.
*/
static void
system_samplescangetsamplesize(PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples)
{
Node *pctnode;
float4 samplefract;
/* Try to extract an estimate for the sample percentage */
pctnode = (Node *) linitial(paramexprs);
pctnode = estimate_expression_value(root, pctnode);
if (IsA(pctnode, Const) &&
!((Const *) pctnode)->constisnull)
{
samplefract = DatumGetFloat4(((Const *) pctnode)->constvalue);
if (samplefract >= 0 && samplefract <= 100 && !isnan(samplefract))
samplefract /= 100.0f;
else
{
/* Default samplefract if the value is bogus */
samplefract = 0.1f;
}
}
else
{
/* Default samplefract if we didn't obtain a non-null Const */
samplefract = 0.1f;
}
/* We'll visit a sample of the pages ... */
*pages = clamp_row_est(baserel->pages * samplefract);
/* ... and hopefully get a representative number of tuples from them */
*tuples = clamp_row_est(baserel->tuples * samplefract);
}
/*
* Initialize during executor setup.
*/
static void
system_initsamplescan(SampleScanState *node, int eflags)
{
node->tsm_state = palloc0(sizeof(SystemSamplerData));
}
/*
* Examine parameters and prepare for a sample scan.
*/
static void
system_beginsamplescan(SampleScanState *node,
Datum *params,
int nparams,
uint32 seed)
{
SystemSamplerData *sampler = (SystemSamplerData *) node->tsm_state;
double percent = DatumGetFloat4(params[0]);
if (percent < 0 || percent > 100 || isnan(percent))
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("invalid sample size"),
errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
errmsg("sample percentage must be between 0 and 100")));
sampler = palloc0(sizeof(SystemSamplerData));
/* Remember initial values for reinit */
/*
* The cutoff is sample probability times (PG_UINT32_MAX + 1); we have to
* store that as a uint64, of course. Note that this gives strictly
* correct behavior at the limits of zero or one probability.
*/
sampler->cutoff = rint(((double) PG_UINT32_MAX + 1) * percent / 100);
sampler->seed = seed;
sampler->nblocks = scan->rs_nblocks;
sampler->samplesize = 1 + (int) (sampler->nblocks * (percent / 100.0));
sampler->nextblock = 0;
sampler->lt = InvalidOffsetNumber;
BlockSampler_Init(&sampler->bs, sampler->nblocks, sampler->samplesize,
sampler->seed);
tsdesc->tsmdata = (void *) sampler;
PG_RETURN_VOID();
/*
* Bulkread buffer access strategy probably makes sense unless we're
* scanning a very small fraction of the table. The 1% cutoff here is a
* guess. We should use pagemode visibility checking, since we scan all
* tuples on each selected page.
*/
node->use_bulkread = (percent >= 1);
node->use_pagemode = true;
}
/*
* Get next block number or InvalidBlockNumber when we're done.
* Select next block to sample.
*/
static BlockNumber
system_nextsampleblock(SampleScanState *node)
{
SystemSamplerData *sampler = (SystemSamplerData *) node->tsm_state;
HeapScanDesc scan = node->ss.ss_currentScanDesc;
BlockNumber nextblock = sampler->nextblock;
uint32 hashinput[2];
/*
* We compute the hash by applying hash_any to an array of 2 uint32's
* containing the block number and seed. This is efficient to set up, and
* with the current implementation of hash_any, it gives
* machine-independent results, which is a nice property for regression
* testing.
*
* These words in the hash input are the same throughout the block:
*/
hashinput[1] = sampler->seed;
/*
* Loop over block numbers until finding suitable block or reaching end of
* relation.
*/
for (; nextblock < scan->rs_nblocks; nextblock++)
{
uint32 hash;
hashinput[0] = nextblock;
hash = DatumGetUInt32(hash_any((const unsigned char *) hashinput,
(int) sizeof(hashinput)));
if (hash < sampler->cutoff)
break;
}
if (nextblock < scan->rs_nblocks)
{
/* Found a suitable block; remember where we should start next time */
sampler->nextblock = nextblock + 1;
return nextblock;
}
/* Done, but let's reset nextblock to 0 for safety. */
sampler->nextblock = 0;
return InvalidBlockNumber;
}
/*
* Select next sampled tuple in current block.
*
* Uses the same logic as ANALYZE for picking the random blocks.
* In block sampling, we just want to sample all the tuples in each selected
* block.
*
* It is OK here to return an offset without knowing if the tuple is visible
* (or even exists); nodeSamplescan.c will deal with that.
*
* When we reach end of the block, return InvalidOffsetNumber which tells
* SampleScan to go to next block.
*/
Datum
tsm_system_nextblock(PG_FUNCTION_ARGS)
static OffsetNumber
system_nextsampletuple(SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
BlockNumber blockno;
if (!BlockSampler_HasMore(&sampler->bs))
PG_RETURN_UINT32(InvalidBlockNumber);
blockno = BlockSampler_Next(&sampler->bs);
PG_RETURN_UINT32(blockno);
}
/*
* Get next tuple offset in current block or InvalidOffsetNumber if we are done
* with this block.
*/
Datum
tsm_system_nexttuple(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
OffsetNumber maxoffset = PG_GETARG_UINT16(2);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
SystemSamplerData *sampler = (SystemSamplerData *) node->tsm_state;
OffsetNumber tupoffset = sampler->lt;
/* Advance to next possible offset on page */
if (tupoffset == InvalidOffsetNumber)
tupoffset = FirstOffsetNumber;
else
tupoffset++;
/* Done? */
if (tupoffset > maxoffset)
tupoffset = InvalidOffsetNumber;
sampler->lt = tupoffset;
PG_RETURN_UINT16(tupoffset);
}
/*
* Cleanup method.
*/
Datum
tsm_system_end(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
pfree(tsdesc->tsmdata);
PG_RETURN_VOID();
}
/*
* Reset state (called by ReScan).
*/
Datum
tsm_system_reset(PG_FUNCTION_ARGS)
{
TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
SystemSamplerData *sampler = (SystemSamplerData *) tsdesc->tsmdata;
sampler->lt = InvalidOffsetNumber;
BlockSampler_Init(&sampler->bs, sampler->nblocks, sampler->samplesize,
sampler->seed);
PG_RETURN_VOID();
}
/*
* Costing function.
*/
Datum
tsm_system_cost(PG_FUNCTION_ARGS)
{
PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
Path *path = (Path *) PG_GETARG_POINTER(1);
RelOptInfo *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
List *args = (List *) PG_GETARG_POINTER(3);
BlockNumber *pages = (BlockNumber *) PG_GETARG_POINTER(4);
double *tuples = (double *) PG_GETARG_POINTER(5);
Node *pctnode;
float4 samplesize;
pctnode = linitial(args);
pctnode = estimate_expression_value(root, pctnode);
if (IsA(pctnode, RelabelType))
pctnode = (Node *) ((RelabelType *) pctnode)->arg;
if (IsA(pctnode, Const))
{
samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
samplesize /= 100.0;
}
else
{
/* Default samplesize if the estimation didn't return Const. */
samplesize = 0.1f;
}
*pages = baserel->pages * samplesize;
*tuples = path->rows * samplesize;
path->rows = *tuples;
PG_RETURN_VOID();
return tupoffset;
}

355
src/backend/access/tablesample/tablesample.c
View File

@ -1,7 +1,7 @@
/*-------------------------------------------------------------------------
*
* tablesample.c
* TABLESAMPLE internal API
* Support functions for TABLESAMPLE feature
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
@ -10,356 +10,31 @@
* IDENTIFICATION
* src/backend/access/tablesample/tablesample.c
*
* TABLESAMPLE is the SQL standard clause for sampling the relations.
*
* The API is interface between the Executor and the TABLESAMPLE Methods.
*
* TABLESAMPLE Methods are implementations of actual sampling algorithms which
* can be used for returning a sample of the source relation.
* Methods don't read the table directly but are asked for block number and
* tuple offset which they want to examine (or return) and the tablesample
* interface implemented here does the reading for them.
*
* We currently only support sampling of the physical relations, but in the
* future we might extend the API to support subqueries as well.
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/tablesample.h"
#include "catalog/pg_tablesample_method.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/predicate.h"
#include "utils/rel.h"
#include "utils/tqual.h"
static bool SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan);
#include "access/tsmapi.h"
/*
* Initialize the TABLESAMPLE Descriptor and the TABLESAMPLE Method.
* GetTsmRoutine --- get a TsmRoutine struct by invoking the handler.
*
* This is a convenience routine that's just meant to check for errors.
*/
TableSampleDesc *
tablesample_init(SampleScanState *scanstate, TableSampleClause *tablesample)
TsmRoutine *
GetTsmRoutine(Oid tsmhandler)
{
FunctionCallInfoData fcinfo;
int i;
List *args = tablesample->args;
ListCell *arg;
ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
TableSampleDesc *tsdesc = (TableSampleDesc *) palloc0(sizeof(TableSampleDesc));
Datum datum;
TsmRoutine *routine;
/* Load functions */
fmgr_info(tablesample->tsminit, &(tsdesc->tsminit));
fmgr_info(tablesample->tsmnextblock, &(tsdesc->tsmnextblock));
fmgr_info(tablesample->tsmnexttuple, &(tsdesc->tsmnexttuple));
if (OidIsValid(tablesample->tsmexaminetuple))
fmgr_info(tablesample->tsmexaminetuple, &(tsdesc->tsmexaminetuple));
else
tsdesc->tsmexaminetuple.fn_oid = InvalidOid;
fmgr_info(tablesample->tsmreset, &(tsdesc->tsmreset));
fmgr_info(tablesample->tsmend, &(tsdesc->tsmend));
datum = OidFunctionCall1(tsmhandler, PointerGetDatum(NULL));
routine = (TsmRoutine *) DatumGetPointer(datum);
InitFunctionCallInfoData(fcinfo, &tsdesc->tsminit,
list_length(args) + 2,
InvalidOid, NULL, NULL);
if (routine == NULL || !IsA(routine, TsmRoutine))
elog(ERROR, "tablesample handler function %u did not return a TsmRoutine struct",
tsmhandler);
tsdesc->tupDesc = scanstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
tsdesc->heapScan = scanstate->ss.ss_currentScanDesc;
/* First argument for init function is always TableSampleDesc */
fcinfo.arg[0] = PointerGetDatum(tsdesc);
fcinfo.argnull[0] = false;
/*
* Second arg for init function is always REPEATABLE.
*
* If tablesample->repeatable is NULL then REPEATABLE clause was not
* specified, and we insert a random value as default.
*
* When specified, the expression cannot evaluate to NULL.
*/
if (tablesample->repeatable)
{
ExprState *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
(PlanState *) scanstate);
fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
&fcinfo.argnull[1], NULL);
if (fcinfo.argnull[1])
ereport(ERROR,
(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
errmsg("REPEATABLE clause must be NOT NULL numeric value")));
}
else
{
fcinfo.arg[1] = UInt32GetDatum(random());
fcinfo.argnull[1] = false;
}
/* Rest of the arguments come from user. */
i = 2;
foreach(arg, args)
{
Expr *argexpr = (Expr *) lfirst(arg);
ExprState *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
&fcinfo.argnull[i], NULL);
i++;
}
Assert(i == fcinfo.nargs);
(void) FunctionCallInvoke(&fcinfo);
return tsdesc;
}
/*
* Get next tuple from TABLESAMPLE Method.
*/
HeapTuple
tablesample_getnext(TableSampleDesc *desc)
{
HeapScanDesc scan = desc->heapScan;
HeapTuple tuple = &(scan->rs_ctup);
bool pagemode = scan->rs_pageatatime;
BlockNumber blockno;
Page page;
bool page_all_visible;
ItemId itemid;
OffsetNumber tupoffset,
maxoffset;
if (!scan->rs_inited)
{
/*
* return null immediately if relation is empty
*/
if (scan->rs_nblocks == 0)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return NULL;
}
blockno = DatumGetInt32(FunctionCall1(&desc->tsmnextblock,
PointerGetDatum(desc)));
if (!BlockNumberIsValid(blockno))
{
tuple->t_data = NULL;
return NULL;
}
heapgetpage(scan, blockno);
scan->rs_inited = true;
}
else
{
/* continue from previously returned page/tuple */
blockno = scan->rs_cblock; /* current page */
}
/*
* When pagemode is disabled, the scan will do visibility checks for each
* tuple it finds so the buffer needs to be locked.
*/
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
page = (Page) BufferGetPage(scan->rs_cbuf);
page_all_visible = PageIsAllVisible(page);
maxoffset = PageGetMaxOffsetNumber(page);
for (;;)
{
CHECK_FOR_INTERRUPTS();
tupoffset = DatumGetUInt16(FunctionCall3(&desc->tsmnexttuple,
PointerGetDatum(desc),
UInt32GetDatum(blockno),
UInt16GetDatum(maxoffset)));
if (OffsetNumberIsValid(tupoffset))
{
bool visible;
bool found;
/* Skip invalid tuple pointers. */
itemid = PageGetItemId(page, tupoffset);
if (!ItemIdIsNormal(itemid))
continue;
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
tuple->t_len = ItemIdGetLength(itemid);
ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
if (page_all_visible)
visible = true;
else
visible = SampleTupleVisible(tuple, tupoffset, scan);
/*
* Let the sampling method examine the actual tuple and decide if
* we should return it.
*
* Note that we let it examine even invisible tuples for
* statistical purposes, but not return them since user should
* never see invisible tuples.
*/
if (OidIsValid(desc->tsmexaminetuple.fn_oid))
{
found = DatumGetBool(FunctionCall4(&desc->tsmexaminetuple,
PointerGetDatum(desc),
UInt32GetDatum(blockno),
PointerGetDatum(tuple),
BoolGetDatum(visible)));
/* Should not happen if sampling method is well written. */
if (found && !visible)
elog(ERROR, "Sampling method wanted to return invisible tuple");
}
else
found = visible;
/* Found visible tuple, return it. */
if (found)
{
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
break;
}
else
{
/* Try next tuple from same page. */
continue;
}
}
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
blockno = DatumGetInt32(FunctionCall1(&desc->tsmnextblock,
PointerGetDatum(desc)));
/*
* Report our new scan position for synchronization purposes. We don't
* do that when moving backwards, however. That would just mess up any
* other forward-moving scanners.
*
* Note: we do this before checking for end of scan so that the final
* state of the position hint is back at the start of the rel. That's
* not strictly necessary, but otherwise when you run the same query
* multiple times the starting position would shift a little bit
* backwards on every invocation, which is confusing. We don't
* guarantee any specific ordering in general, though.
*/
if (scan->rs_syncscan)
ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
blockno : scan->rs_startblock);
/*
* Reached end of scan.
*/
if (!BlockNumberIsValid(blockno))
{
if (BufferIsValid(scan->rs_cbuf))
ReleaseBuffer(scan->rs_cbuf);
scan->rs_cbuf = InvalidBuffer;
scan->rs_cblock = InvalidBlockNumber;
tuple->t_data = NULL;
scan->rs_inited = false;
return NULL;
}
heapgetpage(scan, blockno);
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
page = (Page) BufferGetPage(scan->rs_cbuf);
page_all_visible = PageIsAllVisible(page);
maxoffset = PageGetMaxOffsetNumber(page);
}
pgstat_count_heap_getnext(scan->rs_rd);
return &(scan->rs_ctup);
}
/*
* Reset the sampling to starting state
*/
void
tablesample_reset(TableSampleDesc *desc)
{
(void) FunctionCall1(&desc->tsmreset, PointerGetDatum(desc));
}
/*
* Signal the sampling method that the scan has finished.
*/
void
tablesample_end(TableSampleDesc *desc)
{
(void) FunctionCall1(&desc->tsmend, PointerGetDatum(desc));
}
/*
* Check visibility of the tuple.
*/
static bool
SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
{
/*
* If this scan is reading whole pages at a time, there is already
* visibility info present in rs_vistuples so we can just search it for
* the tupoffset.
*/
if (scan->rs_pageatatime)
{
int start = 0,
end = scan->rs_ntuples - 1;
/*
* Do the binary search over rs_vistuples, it's already sorted by
* OffsetNumber so we don't need to do any sorting ourselves here.
*
* We could use bsearch() here but it's slower for integers because of
* the function call overhead and because it needs boiler plate code
* it would not save us anything code-wise anyway.
*/
while (start <= end)
{
int mid = start + (end - start) / 2;
OffsetNumber curoffset = scan->rs_vistuples[mid];
if (curoffset == tupoffset)
return true;
else if (curoffset > tupoffset)
end = mid - 1;
else
start = mid + 1;
}
return false;
}
else
{
/* No pagemode, we have to check the tuple itself. */
Snapshot snapshot = scan->rs_snapshot;
Buffer buffer = scan->rs_cbuf;
bool visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
CheckForSerializableConflictOut(visible, scan->rs_rd, tuple, buffer,
snapshot);
return visible;
}
return routine;
}

5
src/backend/catalog/Makefile
View File

@ -40,8 +40,9 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
pg_ts_parser.h pg_ts_template.h pg_extension.h \
pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
pg_foreign_table.h pg_policy.h pg_replication_origin.h \
pg_tablesample_method.h pg_default_acl.h pg_seclabel.h pg_shseclabel.h \
pg_collation.h pg_range.h pg_transform.h toasting.h indexing.h \
pg_default_acl.h pg_seclabel.h pg_shseclabel.h \
pg_collation.h pg_range.h pg_transform.h \
toasting.h indexing.h \
)
# location of Catalog.pm

8
src/backend/catalog/dependency.c
View File

@ -1911,6 +1911,14 @@ find_expr_references_walker(Node *node,
context->addrs);
}
}
else if (IsA(node, TableSampleClause))
{
TableSampleClause *tsc = (TableSampleClause *) node;
add_object_address(OCLASS_PROC, tsc->tsmhandler, 0,
context->addrs);
/* fall through to examine arguments */
}
return expression_tree_walker(node, find_expr_references_walker,
(void *) context);

107
src/backend/commands/explain.c
View File

@ -96,6 +96,8 @@ static void show_sort_group_keys(PlanState *planstate, const char *qlabel,
List *ancestors, ExplainState *es);
static void show_sortorder_options(StringInfo buf, Node *sortexpr,
Oid sortOperator, Oid collation, bool nullsFirst);
static void show_tablesample(TableSampleClause *tsc, PlanState *planstate,
List *ancestors, ExplainState *es);
static void show_sort_info(SortState *sortstate, ExplainState *es);
static void show_hash_info(HashState *hashstate, ExplainState *es);
static void show_tidbitmap_info(BitmapHeapScanState *planstate,
@ -116,7 +118,7 @@ static void ExplainMemberNodes(List *plans, PlanState **planstates,
static void ExplainSubPlans(List *plans, List *ancestors,
const char *relationship, ExplainState *es);
static void ExplainCustomChildren(CustomScanState *css,
List *ancestors, ExplainState *es);
List *ancestors, ExplainState *es);
static void ExplainProperty(const char *qlabel, const char *value,
bool numeric, ExplainState *es);
static void ExplainOpenGroup(const char *objtype, const char *labelname,
@ -730,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
switch (nodeTag(plan))
{
case T_SeqScan:
case T_SampleScan:
case T_IndexScan:
case T_IndexOnlyScan:
case T_BitmapHeapScan:
@ -739,7 +742,6 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
case T_ValuesScan:
case T_CteScan:
case T_WorkTableScan:
case T_SampleScan:
*rels_used = bms_add_member(*rels_used,
((Scan *) plan)->scanrelid);
break;
@ -935,6 +937,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
case T_SeqScan:
pname = sname = "Seq Scan";
break;
case T_SampleScan:
pname = sname = "Sample Scan";
break;
case T_IndexScan:
pname = sname = "Index Scan";
break;
@ -976,23 +981,6 @@ ExplainNode(PlanState *planstate, List *ancestors,
else
pname = sname;
break;
case T_SampleScan:
{
/*
* Fetch the tablesample method name from RTE.
*
* It would be nice to also show parameters, but since we
* support arbitrary expressions as parameter it might get
* quite messy.
*/
RangeTblEntry *rte;
rte = rt_fetch(((SampleScan *) plan)->scanrelid, es->rtable);
custom_name = get_tablesample_method_name(rte->tablesample->tsmid);
pname = psprintf("Sample Scan (%s)", custom_name);
sname = "Sample Scan";
}
break;
case T_Material:
pname = sname = "Materialize";
break;
@ -1101,6 +1089,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
switch (nodeTag(plan))
{
case T_SeqScan:
case T_SampleScan:
case T_BitmapHeapScan:
case T_TidScan:
case T_SubqueryScan:
@ -1115,9 +1104,6 @@ ExplainNode(PlanState *planstate, List *ancestors,
if (((Scan *) plan)->scanrelid > 0)
ExplainScanTarget((Scan *) plan, es);
break;
case T_SampleScan:
ExplainScanTarget((Scan *) plan, es);
break;
case T_IndexScan:
{
IndexScan *indexscan = (IndexScan *) plan;
@ -1363,12 +1349,15 @@ ExplainNode(PlanState *planstate, List *ancestors,
if (es->analyze)
show_tidbitmap_info((BitmapHeapScanState *) planstate, es);
break;
case T_SampleScan:
show_tablesample(((SampleScan *) plan)->tablesample,
planstate, ancestors, es);
/* FALL THRU to print additional fields the same as SeqScan */
case T_SeqScan:
case T_ValuesScan:
case T_CteScan:
case T_WorkTableScan:
case T_SubqueryScan:
case T_SampleScan:
show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
if (plan->qual)
show_instrumentation_count("Rows Removed by Filter", 1,
@ -2109,6 +2098,72 @@ show_sortorder_options(StringInfo buf, Node *sortexpr,
}
}
/*
* Show TABLESAMPLE properties
*/
static void
show_tablesample(TableSampleClause *tsc, PlanState *planstate,
List *ancestors, ExplainState *es)
{
List *context;
bool useprefix;
char *method_name;
List *params = NIL;
char *repeatable;
ListCell *lc;
/* Set up deparsing context */
context = set_deparse_context_planstate(es->deparse_cxt,
(Node *) planstate,
ancestors);
useprefix = list_length(es->rtable) > 1;
/* Get the tablesample method name */
method_name = get_func_name(tsc->tsmhandler);
/* Deparse parameter expressions */
foreach(lc, tsc->args)
{
Node *arg = (Node *) lfirst(lc);
params = lappend(params,
deparse_expression(arg, context,
useprefix, false));
}
if (tsc->repeatable)
repeatable = deparse_expression((Node *) tsc->repeatable, context,
useprefix, false);
else
repeatable = NULL;
/* Print results */
if (es->format == EXPLAIN_FORMAT_TEXT)
{
bool first = true;
appendStringInfoSpaces(es->str, es->indent * 2);
appendStringInfo(es->str, "Sampling: %s (", method_name);
foreach(lc, params)
{
if (!first)
appendStringInfoString(es->str, ", ");
appendStringInfoString(es->str, (const char *) lfirst(lc));
first = false;
}
appendStringInfoChar(es->str, ')');
if (repeatable)
appendStringInfo(es->str, " REPEATABLE (%s)", repeatable);
appendStringInfoChar(es->str, '\n');
}
else
{
ExplainPropertyText("Sampling Method", method_name, es);
ExplainPropertyList("Sampling Parameters", params, es);
if (repeatable)
ExplainPropertyText("Repeatable Seed", repeatable, es);
}
}
/*
* If it's EXPLAIN ANALYZE, show tuplesort stats for a sort node
*/
@ -2366,13 +2421,13 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
switch (nodeTag(plan))
{
case T_SeqScan:
case T_SampleScan:
case T_IndexScan:
case T_IndexOnlyScan:
case T_BitmapHeapScan:
case T_TidScan:
case T_ForeignScan:
case T_CustomScan:
case T_SampleScan:
case T_ModifyTable:
/* Assert it's on a real relation */
Assert(rte->rtekind == RTE_RELATION);
@ -2663,9 +2718,9 @@ ExplainCustomChildren(CustomScanState *css, List *ancestors, ExplainState *es)
{
ListCell *cell;
const char *label =
(list_length(css->custom_ps) != 1 ? "children" : "child");
(list_length(css->custom_ps) != 1 ? "children" : "child");
foreach (cell, css->custom_ps)
foreach(cell, css->custom_ps)
ExplainNode((PlanState *) lfirst(cell), ancestors, label, NULL, es);
}

7
src/backend/executor/execAmi.c
View File

@ -463,6 +463,10 @@ ExecSupportsBackwardScan(Plan *node)
case T_CteScan:
return TargetListSupportsBackwardScan(node->targetlist);
case T_SampleScan:
/* Simplify life for tablesample methods by disallowing this */
return false;
case T_IndexScan:
return IndexSupportsBackwardScan(((IndexScan *) node)->indexid) &&
TargetListSupportsBackwardScan(node->targetlist);
@ -485,9 +489,6 @@ ExecSupportsBackwardScan(Plan *node)
}
return false;
case T_SampleScan:
return false;
case T_Material:
case T_Sort:
/* these don't evaluate tlist */

441
src/backend/executor/nodeSamplescan.c
View File

@ -3,7 +3,7 @@
* nodeSamplescan.c
* Support routines for sample scans of relations (table sampling).
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
@ -14,22 +14,23 @@
*/
#include "postgres.h"
#include "access/tablesample.h"
#include "access/hash.h"
#include "access/relscan.h"
#include "access/tsmapi.h"
#include "executor/executor.h"
#include "executor/nodeSamplescan.h"
#include "miscadmin.h"
#include "parser/parsetree.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/predicate.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
static void InitScanRelation(SampleScanState *node, EState *estate,
int eflags, TableSampleClause *tablesample);
static void InitScanRelation(SampleScanState *node, EState *estate, int eflags);
static TupleTableSlot *SampleNext(SampleScanState *node);
static void tablesample_init(SampleScanState *scanstate);
static HeapTuple tablesample_getnext(SampleScanState *scanstate);
static bool SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset,
HeapScanDesc scan);
/* ----------------------------------------------------------------
* Scan Support
@ -45,23 +46,26 @@ static TupleTableSlot *SampleNext(SampleScanState *node);
static TupleTableSlot *
SampleNext(SampleScanState *node)
{
TupleTableSlot *slot;
TableSampleDesc *tsdesc;
HeapTuple tuple;
TupleTableSlot *slot;
/*
* get information from the scan state
* if this is first call within a scan, initialize
*/
slot = node->ss.ss_ScanTupleSlot;
tsdesc = node->tsdesc;
if (!node->begun)
tablesample_init(node);
tuple = tablesample_getnext(tsdesc);
/*
* get the next tuple, and store it in our result slot
*/
tuple = tablesample_getnext(node);
slot = node->ss.ss_ScanTupleSlot;
if (tuple)
ExecStoreTuple(tuple, /* tuple to store */
slot, /* slot to store in */
tsdesc->heapScan->rs_cbuf, /* buffer associated
* with this tuple */
node->ss.ss_currentScanDesc->rs_cbuf, /* tuple's buffer */
false); /* don't pfree this pointer */
else
ExecClearTuple(slot);
@ -75,7 +79,10 @@ SampleNext(SampleScanState *node)
static bool
SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
{
/* No need to recheck for SampleScan */
/*
* No need to recheck for SampleScan, since like SeqScan we don't pass any
* checkable keys to heap_beginscan.
*/
return true;
}
@ -103,8 +110,7 @@ ExecSampleScan(SampleScanState *node)
* ----------------------------------------------------------------
*/
static void
InitScanRelation(SampleScanState *node, EState *estate, int eflags,
TableSampleClause *tablesample)
InitScanRelation(SampleScanState *node, EState *estate, int eflags)
{
Relation currentRelation;
@ -113,19 +119,13 @@ InitScanRelation(SampleScanState *node, EState *estate, int eflags,
* open that relation and acquire appropriate lock on it.
*/
currentRelation = ExecOpenScanRelation(estate,
((SampleScan *) node->ss.ps.plan)->scanrelid,
((SampleScan *) node->ss.ps.plan)->scan.scanrelid,
eflags);
node->ss.ss_currentRelation = currentRelation;
/*
* Even though we aren't going to do a conventional seqscan, it is useful
* to create a HeapScanDesc --- many of the fields in it are usable.
*/
node->ss.ss_currentScanDesc =
heap_beginscan_sampling(currentRelation, estate->es_snapshot, 0, NULL,
tablesample->tsmseqscan,
tablesample->tsmpagemode);
/* we won't set up the HeapScanDesc till later */
node->ss.ss_currentScanDesc = NULL;
/* and report the scan tuple slot's rowtype */
ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
@ -140,12 +140,11 @@ SampleScanState *
ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
{
SampleScanState *scanstate;
RangeTblEntry *rte = rt_fetch(node->scanrelid,
estate->es_range_table);
TableSampleClause *tsc = node->tablesample;
TsmRoutine *tsm;
Assert(outerPlan(node) == NULL);
Assert(innerPlan(node) == NULL);
Assert(rte->tablesample != NULL);
/*
* create state structure
@ -165,10 +164,17 @@ ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
* initialize child expressions
*/
scanstate->ss.ps.targetlist = (List *)
ExecInitExpr((Expr *) node->plan.targetlist,
ExecInitExpr((Expr *) node->scan.plan.targetlist,
(PlanState *) scanstate);
scanstate->ss.ps.qual = (List *)
ExecInitExpr((Expr *) node->plan.qual,
ExecInitExpr((Expr *) node->scan.plan.qual,
(PlanState *) scanstate);
scanstate->args = (List *)
ExecInitExpr((Expr *) tsc->args,
(PlanState *) scanstate);
scanstate->repeatable =
ExecInitExpr(tsc->repeatable,
(PlanState *) scanstate);
/*
@ -180,7 +186,7 @@ ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
/*
* initialize scan relation
*/
InitScanRelation(scanstate, estate, eflags, rte->tablesample);
InitScanRelation(scanstate, estate, eflags);
scanstate->ss.ps.ps_TupFromTlist = false;
@ -190,7 +196,25 @@ ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
ExecAssignScanProjectionInfo(&scanstate->ss);
scanstate->tsdesc = tablesample_init(scanstate, rte->tablesample);
/*
* If we don't have a REPEATABLE clause, select a random seed. We want to
* do this just once, since the seed shouldn't change over rescans.
*/
if (tsc->repeatable == NULL)
scanstate->seed = random();
/*
* Finally, initialize the TABLESAMPLE method handler.
*/
tsm = GetTsmRoutine(tsc->tsmhandler);
scanstate->tsmroutine = tsm;
scanstate->tsm_state = NULL;
if (tsm->InitSampleScan)
tsm->InitSampleScan(scanstate, eflags);
/* We'll do BeginSampleScan later; we can't evaluate params yet */
scanstate->begun = false;
return scanstate;
}
@ -207,7 +231,8 @@ ExecEndSampleScan(SampleScanState *node)
/*
* Tell sampling function that we finished the scan.
*/
tablesample_end(node->tsdesc);
if (node->tsmroutine->EndSampleScan)
node->tsmroutine->EndSampleScan(node);
/*
* Free the exprcontext
@ -223,7 +248,8 @@ ExecEndSampleScan(SampleScanState *node)
/*
* close heap scan
*/
heap_endscan(node->ss.ss_currentScanDesc);
if (node->ss.ss_currentScanDesc)
heap_endscan(node->ss.ss_currentScanDesc);
/*
* close the heap relation.
@ -231,11 +257,6 @@ ExecEndSampleScan(SampleScanState *node)
ExecCloseScanRelation(node->ss.ss_currentRelation);
}
/* ----------------------------------------------------------------
* Join Support
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* ExecReScanSampleScan
*
@ -246,12 +267,336 @@ ExecEndSampleScan(SampleScanState *node)
void
ExecReScanSampleScan(SampleScanState *node)
{
heap_rescan(node->ss.ss_currentScanDesc, NULL);
/*
* Tell sampling function to reset its state for rescan.
*/
tablesample_reset(node->tsdesc);
/* Remember we need to do BeginSampleScan again (if we did it at all) */
node->begun = false;
ExecScanReScan(&node->ss);
}
/*
* Initialize the TABLESAMPLE method: evaluate params and call BeginSampleScan.
*/
static void
tablesample_init(SampleScanState *scanstate)
{
TsmRoutine *tsm = scanstate->tsmroutine;
ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
Datum *params;
Datum datum;
bool isnull;
uint32 seed;
bool allow_sync;
int i;
ListCell *arg;
params = (Datum *) palloc(list_length(scanstate->args) * sizeof(Datum));
i = 0;
foreach(arg, scanstate->args)
{
ExprState *argstate = (ExprState *) lfirst(arg);
params[i] = ExecEvalExprSwitchContext(argstate,
econtext,
&isnull,
NULL);
if (isnull)
ereport(ERROR,
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
errmsg("TABLESAMPLE parameter cannot be null")));
i++;
}
if (scanstate->repeatable)
{
datum = ExecEvalExprSwitchContext(scanstate->repeatable,
econtext,
&isnull,
NULL);
if (isnull)
ereport(ERROR,
(errcode(ERRCODE_INVALID_TABLESAMPLE_REPEAT),
errmsg("TABLESAMPLE REPEATABLE parameter cannot be null")));
/*
* The REPEATABLE parameter has been coerced to float8 by the parser.
* The reason for using float8 at the SQL level is that it will
* produce unsurprising results both for users used to databases that
* accept only integers in the REPEATABLE clause and for those who
* might expect that REPEATABLE works like setseed() (a float in the
* range from -1 to 1).
*
* We use hashfloat8() to convert the supplied value into a suitable
* seed. For regression-testing purposes, that has the convenient
* property that REPEATABLE(0) gives a machine-independent result.
*/
seed = DatumGetUInt32(DirectFunctionCall1(hashfloat8, datum));
}
else
{
/* Use the seed selected by ExecInitSampleScan */
seed = scanstate->seed;
}
/* Set default values for params that BeginSampleScan can adjust */
scanstate->use_bulkread = true;
scanstate->use_pagemode = true;
/* Let tablesample method do its thing */
tsm->BeginSampleScan(scanstate,
params,
list_length(scanstate->args),
seed);
/* We'll use syncscan if there's no NextSampleBlock function */
allow_sync = (tsm->NextSampleBlock == NULL);
/* Now we can create or reset the HeapScanDesc */
if (scanstate->ss.ss_currentScanDesc == NULL)
{
scanstate->ss.ss_currentScanDesc =
heap_beginscan_sampling(scanstate->ss.ss_currentRelation,
scanstate->ss.ps.state->es_snapshot,
0, NULL,
scanstate->use_bulkread,
allow_sync,
scanstate->use_pagemode);
}
else
{
heap_rescan_set_params(scanstate->ss.ss_currentScanDesc, NULL,
scanstate->use_bulkread,
allow_sync,
scanstate->use_pagemode);
}
pfree(params);
/* And we're initialized. */
scanstate->begun = true;
}
/*
* Get next tuple from TABLESAMPLE method.
*
* Note: an awful lot of this is copied-and-pasted from heapam.c. It would
* perhaps be better to refactor to share more code.
*/
static HeapTuple
tablesample_getnext(SampleScanState *scanstate)
{
TsmRoutine *tsm = scanstate->tsmroutine;
HeapScanDesc scan = scanstate->ss.ss_currentScanDesc;
HeapTuple tuple = &(scan->rs_ctup);
Snapshot snapshot = scan->rs_snapshot;
bool pagemode = scan->rs_pageatatime;
BlockNumber blockno;
Page page;
bool all_visible;
OffsetNumber maxoffset;
if (!scan->rs_inited)
{
/*
* return null immediately if relation is empty
*/
if (scan->rs_nblocks == 0)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return NULL;
}
if (tsm->NextSampleBlock)
{
blockno = tsm->NextSampleBlock(scanstate);
if (!BlockNumberIsValid(blockno))
{
tuple->t_data = NULL;
return NULL;
}
}
else
blockno = scan->rs_startblock;
Assert(blockno < scan->rs_nblocks);
heapgetpage(scan, blockno);
scan->rs_inited = true;
}
else
{
/* continue from previously returned page/tuple */
blockno = scan->rs_cblock; /* current page */
}
/*
* When not using pagemode, we must lock the buffer during tuple
* visibility checks.
*/
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
page = (Page) BufferGetPage(scan->rs_cbuf);
all_visible = PageIsAllVisible(page) && !snapshot->takenDuringRecovery;
maxoffset = PageGetMaxOffsetNumber(page);
for (;;)
{
OffsetNumber tupoffset;
bool finished;
CHECK_FOR_INTERRUPTS();
/* Ask the tablesample method which tuples to check on this page. */
tupoffset = tsm->NextSampleTuple(scanstate,
blockno,
maxoffset);
if (OffsetNumberIsValid(tupoffset))
{
ItemId itemid;
bool visible;
/* Skip invalid tuple pointers. */
itemid = PageGetItemId(page, tupoffset);
if (!ItemIdIsNormal(itemid))
continue;
tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
tuple->t_len = ItemIdGetLength(itemid);
ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
if (all_visible)
visible = true;
else
visible = SampleTupleVisible(tuple, tupoffset, scan);
/* in pagemode, heapgetpage did this for us */
if (!pagemode)
CheckForSerializableConflictOut(visible, scan->rs_rd, tuple,
scan->rs_cbuf, snapshot);
if (visible)
{
/* Found visible tuple, return it. */
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
break;
}
else
{
/* Try next tuple from same page. */
continue;
}
}
/*
* if we get here, it means we've exhausted the items on this page and
* it's time to move to the next.
*/
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
if (tsm->NextSampleBlock)
{
blockno = tsm->NextSampleBlock(scanstate);
Assert(!scan->rs_syncscan);
finished = !BlockNumberIsValid(blockno);
}
else
{
/* Without NextSampleBlock, just do a plain forward seqscan. */
blockno++;
if (blockno >= scan->rs_nblocks)
blockno = 0;
/*
* Report our new scan position for synchronization purposes.
*
* Note: we do this before checking for end of scan so that the
* final state of the position hint is back at the start of the
* rel. That's not strictly necessary, but otherwise when you run
* the same query multiple times the starting position would shift
* a little bit backwards on every invocation, which is confusing.
* We don't guarantee any specific ordering in general, though.
*/
if (scan->rs_syncscan)
ss_report_location(scan->rs_rd, blockno);
finished = (blockno == scan->rs_startblock);
}
/*
* Reached end of scan?
*/
if (finished)
{
if (BufferIsValid(scan->rs_cbuf))
ReleaseBuffer(scan->rs_cbuf);
scan->rs_cbuf = InvalidBuffer;
scan->rs_cblock = InvalidBlockNumber;
tuple->t_data = NULL;
scan->rs_inited = false;
return NULL;
}
Assert(blockno < scan->rs_nblocks);
heapgetpage(scan, blockno);
/* Re-establish state for new page */
if (!pagemode)
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
page = (Page) BufferGetPage(scan->rs_cbuf);
all_visible = PageIsAllVisible(page) && !snapshot->takenDuringRecovery;
maxoffset = PageGetMaxOffsetNumber(page);
}
/* Count successfully-fetched tuples as heap fetches */
pgstat_count_heap_getnext(scan->rs_rd);
return &(scan->rs_ctup);
}
/*
* Check visibility of the tuple.
*/
static bool
SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
{
if (scan->rs_pageatatime)
{
/*
* In pageatatime mode, heapgetpage() already did visibility checks,
* so just look at the info it left in rs_vistuples[].
*
* We use a binary search over the known-sorted array. Note: we could
* save some effort if we insisted that NextSampleTuple select tuples
* in increasing order, but it's not clear that there would be enough
* gain to justify the restriction.
*/
int start = 0,
end = scan->rs_ntuples - 1;
while (start <= end)
{
int mid = (start + end) / 2;
OffsetNumber curoffset = scan->rs_vistuples[mid];
if (tupoffset == curoffset)
return true;
else if (tupoffset < curoffset)
end = mid - 1;
else
start = mid + 1;
}
return false;
}
else
{
/* Otherwise, we have to check the tuple individually. */
return HeapTupleSatisfiesVisibility(tuple,
scan->rs_snapshot,
scan->rs_cbuf);
}
}

115
src/backend/nodes/copyfuncs.c
View File

@ -359,6 +359,27 @@ _copySeqScan(const SeqScan *from)
return newnode;
}
/*
* _copySampleScan
*/
static SampleScan *
_copySampleScan(const SampleScan *from)
{
SampleScan *newnode = makeNode(SampleScan);
/*
* copy node superclass fields
*/
CopyScanFields((const Scan *) from, (Scan *) newnode);
/*
* copy remainder of node
*/
COPY_NODE_FIELD(tablesample);
return newnode;
}
/*
* _copyIndexScan
*/
@ -641,22 +662,6 @@ _copyCustomScan(const CustomScan *from)
return newnode;
}
/*
* _copySampleScan
*/
static SampleScan *
_copySampleScan(const SampleScan *from)
{
SampleScan *newnode = makeNode(SampleScan);
/*
* copy node superclass fields
*/
CopyScanFields((const Scan *) from, (Scan *) newnode);
return newnode;
}
/*
* CopyJoinFields
*
@ -2143,6 +2148,18 @@ _copyRangeTblFunction(const RangeTblFunction *from)
return newnode;
}
static TableSampleClause *
_copyTableSampleClause(const TableSampleClause *from)
{
TableSampleClause *newnode = makeNode(TableSampleClause);
COPY_SCALAR_FIELD(tsmhandler);
COPY_NODE_FIELD(args);
COPY_NODE_FIELD(repeatable);
return newnode;
}
static WithCheckOption *
_copyWithCheckOption(const WithCheckOption *from)
{
@ -2271,40 +2288,6 @@ _copyCommonTableExpr(const CommonTableExpr *from)
return newnode;
}
static RangeTableSample *
_copyRangeTableSample(const RangeTableSample *from)
{
RangeTableSample *newnode = makeNode(RangeTableSample);
COPY_NODE_FIELD(relation);
COPY_STRING_FIELD(method);
COPY_NODE_FIELD(repeatable);
COPY_NODE_FIELD(args);
return newnode;
}
static TableSampleClause *
_copyTableSampleClause(const TableSampleClause *from)
{
TableSampleClause *newnode = makeNode(TableSampleClause);
COPY_SCALAR_FIELD(tsmid);
COPY_SCALAR_FIELD(tsmseqscan);
COPY_SCALAR_FIELD(tsmpagemode);
COPY_SCALAR_FIELD(tsminit);
COPY_SCALAR_FIELD(tsmnextblock);
COPY_SCALAR_FIELD(tsmnexttuple);
COPY_SCALAR_FIELD(tsmexaminetuple);
COPY_SCALAR_FIELD(tsmend);
COPY_SCALAR_FIELD(tsmreset);
COPY_SCALAR_FIELD(tsmcost);
COPY_NODE_FIELD(repeatable);
COPY_NODE_FIELD(args);
return newnode;
}
static A_Expr *
_copyAExpr(const A_Expr *from)
{
@ -2532,6 +2515,20 @@ _copyRangeFunction(const RangeFunction *from)
return newnode;
}
static RangeTableSample *
_copyRangeTableSample(const RangeTableSample *from)
{
RangeTableSample *newnode = makeNode(RangeTableSample);
COPY_NODE_FIELD(relation);
COPY_NODE_FIELD(method);
COPY_NODE_FIELD(args);
COPY_NODE_FIELD(repeatable);
COPY_LOCATION_FIELD(location);
return newnode;
}
static TypeCast *
_copyTypeCast(const TypeCast *from)
{
@ -4237,6 +4234,9 @@ copyObject(const void *from)
case T_SeqScan:
retval = _copySeqScan(from);
break;
case T_SampleScan:
retval = _copySampleScan(from);
break;
case T_IndexScan:
retval = _copyIndexScan(from);
break;
@ -4273,9 +4273,6 @@ copyObject(const void *from)
case T_CustomScan:
retval = _copyCustomScan(from);
break;
case T_SampleScan:
retval = _copySampleScan(from);
break;
case T_Join:
retval = _copyJoin(from);
break;
@ -4897,6 +4894,9 @@ copyObject(const void *from)
case T_RangeFunction:
retval = _copyRangeFunction(from);
break;
case T_RangeTableSample:
retval = _copyRangeTableSample(from);
break;
case T_TypeName:
retval = _copyTypeName(from);
break;
@ -4921,6 +4921,9 @@ copyObject(const void *from)
case T_RangeTblFunction:
retval = _copyRangeTblFunction(from);
break;
case T_TableSampleClause:
retval = _copyTableSampleClause(from);
break;
case T_WithCheckOption:
retval = _copyWithCheckOption(from);
break;
@ -4948,12 +4951,6 @@ copyObject(const void *from)
case T_CommonTableExpr:
retval = _copyCommonTableExpr(from);
break;
case T_RangeTableSample:
retval = _copyRangeTableSample(from);
break;
case T_TableSampleClause:
retval = _copyTableSampleClause(from);
break;
case T_FuncWithArgs:
retval = _copyFuncWithArgs(from);
break;

64
src/backend/nodes/equalfuncs.c
View File

@ -2290,6 +2290,18 @@ _equalRangeFunction(const RangeFunction *a, const RangeFunction *b)
return true;
}
static bool
_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
{
COMPARE_NODE_FIELD(relation);
COMPARE_NODE_FIELD(method);
COMPARE_NODE_FIELD(args);
COMPARE_NODE_FIELD(repeatable);
COMPARE_LOCATION_FIELD(location);
return true;
}
static bool
_equalIndexElem(const IndexElem *a, const IndexElem *b)
{
@ -2428,6 +2440,16 @@ _equalRangeTblFunction(const RangeTblFunction *a, const RangeTblFunction *b)
return true;
}
static bool
_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
{
COMPARE_SCALAR_FIELD(tsmhandler);
COMPARE_NODE_FIELD(args);
COMPARE_NODE_FIELD(repeatable);
return true;
}
static bool
_equalWithCheckOption(const WithCheckOption *a, const WithCheckOption *b)
{
@ -2538,36 +2560,6 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
return true;
}
static bool
_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
{
COMPARE_NODE_FIELD(relation);
COMPARE_STRING_FIELD(method);
COMPARE_NODE_FIELD(repeatable);
COMPARE_NODE_FIELD(args);
return true;
}
static bool
_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
{
COMPARE_SCALAR_FIELD(tsmid);
COMPARE_SCALAR_FIELD(tsmseqscan);
COMPARE_SCALAR_FIELD(tsmpagemode);
COMPARE_SCALAR_FIELD(tsminit);
COMPARE_SCALAR_FIELD(tsmnextblock);
COMPARE_SCALAR_FIELD(tsmnexttuple);
COMPARE_SCALAR_FIELD(tsmexaminetuple);
COMPARE_SCALAR_FIELD(tsmend);
COMPARE_SCALAR_FIELD(tsmreset);
COMPARE_SCALAR_FIELD(tsmcost);
COMPARE_NODE_FIELD(repeatable);
COMPARE_NODE_FIELD(args);
return true;
}
static bool
_equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
{
@ -3260,6 +3252,9 @@ equal(const void *a, const void *b)
case T_RangeFunction:
retval = _equalRangeFunction(a, b);
break;
case T_RangeTableSample:
retval = _equalRangeTableSample(a, b);
break;
case T_TypeName:
retval = _equalTypeName(a, b);
break;
@ -3284,6 +3279,9 @@ equal(const void *a, const void *b)
case T_RangeTblFunction:
retval = _equalRangeTblFunction(a, b);
break;
case T_TableSampleClause:
retval = _equalTableSampleClause(a, b);
break;
case T_WithCheckOption:
retval = _equalWithCheckOption(a, b);
break;
@ -3311,12 +3309,6 @@ equal(const void *a, const void *b)
case T_CommonTableExpr:
retval = _equalCommonTableExpr(a, b);
break;
case T_RangeTableSample:
retval = _equalRangeTableSample(a, b);
break;
case T_TableSampleClause:
retval = _equalTableSampleClause(a, b);
break;
case T_FuncWithArgs:
retval = _equalFuncWithArgs(a, b);
break;

75
src/backend/nodes/nodeFuncs.c
View File

@ -1486,6 +1486,9 @@ exprLocation(const Node *expr)
case T_WindowDef:
loc = ((const WindowDef *) expr)->location;
break;
case T_RangeTableSample:
loc = ((const RangeTableSample *) expr)->location;
break;
case T_TypeName:
loc = ((const TypeName *) expr)->location;
break;
@ -1995,6 +1998,17 @@ expression_tree_walker(Node *node,
return walker(((PlaceHolderInfo *) node)->ph_var, context);
case T_RangeTblFunction:
return walker(((RangeTblFunction *) node)->funcexpr, context);
case T_TableSampleClause:
{
TableSampleClause *tsc = (TableSampleClause *) node;
if (expression_tree_walker((Node *) tsc->args,
walker, context))
return true;
if (walker((Node *) tsc->repeatable, context))
return true;
}
break;
default:
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(node));
@ -2082,13 +2096,8 @@ range_table_walker(List *rtable,
switch (rte->rtekind)
{
case RTE_RELATION:
if (rte->tablesample)
{
if (walker(rte->tablesample->args, context))
return true;
if (walker(rte->tablesample->repeatable, context))
return true;
}
if (walker(rte->tablesample, context))
return true;
break;
case RTE_CTE:
/* nothing to do */
@ -2782,6 +2791,17 @@ expression_tree_mutator(Node *node,
return (Node *) newnode;
}
break;
case T_TableSampleClause:
{
TableSampleClause *tsc = (TableSampleClause *) node;
TableSampleClause *newnode;
FLATCOPY(newnode, tsc, TableSampleClause);
MUTATE(newnode->args, tsc->args, List *);
MUTATE(newnode->repeatable, tsc->repeatable, Expr *);
return (Node *) newnode;
}
break;
default:
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(node));
@ -2868,20 +2888,12 @@ range_table_mutator(List *rtable,
switch (rte->rtekind)
{
case RTE_RELATION:
if (rte->tablesample)
{
CHECKFLATCOPY(newrte->tablesample, rte->tablesample,
TableSampleClause);
MUTATE(newrte->tablesample->args,
newrte->tablesample->args,
List *);
MUTATE(newrte->tablesample->repeatable,
newrte->tablesample->repeatable,
Node *);
}
MUTATE(newrte->tablesample, rte->tablesample,
TableSampleClause *);
/* we don't bother to copy eref, aliases, etc; OK? */
break;
case RTE_CTE:
/* we don't bother to copy eref, aliases, etc; OK? */
/* nothing to do */
break;
case RTE_SUBQUERY:
if (!(flags & QTW_IGNORE_RT_SUBQUERIES))
@ -3316,6 +3328,19 @@ raw_expression_tree_walker(Node *node,
return true;
}
break;
case T_RangeTableSample:
{
RangeTableSample *rts = (RangeTableSample *) node;
if (walker(rts->relation, context))
return true;
/* method name is deemed uninteresting */
if (walker(rts->args, context))
return true;
if (walker(rts->repeatable, context))
return true;
}
break;
case T_TypeName:
{
TypeName *tn = (TypeName *) node;
@ -3380,18 +3405,6 @@ raw_expression_tree_walker(Node *node,
break;
case T_CommonTableExpr:
return walker(((CommonTableExpr *) node)->ctequery, context);
case T_RangeTableSample:
{
RangeTableSample *rts = (RangeTableSample *) node;
if (walker(rts->relation, context))
return true;
if (walker(rts->repeatable, context))
return true;
if (walker(rts->args, context))
return true;
}
break;
default:
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(node));

88
src/backend/nodes/outfuncs.c
View File

@ -444,6 +444,16 @@ _outSeqScan(StringInfo str, const SeqScan *node)
_outScanInfo(str, (const Scan *) node);
}
static void
_outSampleScan(StringInfo str, const SampleScan *node)
{
WRITE_NODE_TYPE("SAMPLESCAN");
_outScanInfo(str, (const Scan *) node);
WRITE_NODE_FIELD(tablesample);
}
static void
_outIndexScan(StringInfo str, const IndexScan *node)
{
@ -591,14 +601,6 @@ _outCustomScan(StringInfo str, const CustomScan *node)
node->methods->TextOutCustomScan(str, node);
}
static void
_outSampleScan(StringInfo str, const SampleScan *node)
{
WRITE_NODE_TYPE("SAMPLESCAN");
_outScanInfo(str, (const Scan *) node);
}
static void
_outJoin(StringInfo str, const Join *node)
{
@ -2478,36 +2480,6 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
WRITE_NODE_FIELD(ctecolcollations);
}
static void
_outRangeTableSample(StringInfo str, const RangeTableSample *node)
{
WRITE_NODE_TYPE("RANGETABLESAMPLE");
WRITE_NODE_FIELD(relation);
WRITE_STRING_FIELD(method);
WRITE_NODE_FIELD(repeatable);
WRITE_NODE_FIELD(args);
}
static void
_outTableSampleClause(StringInfo str, const TableSampleClause *node)
{
WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
WRITE_OID_FIELD(tsmid);
WRITE_BOOL_FIELD(tsmseqscan);
WRITE_BOOL_FIELD(tsmpagemode);
WRITE_OID_FIELD(tsminit);
WRITE_OID_FIELD(tsmnextblock);
WRITE_OID_FIELD(tsmnexttuple);
WRITE_OID_FIELD(tsmexaminetuple);
WRITE_OID_FIELD(tsmend);
WRITE_OID_FIELD(tsmreset);
WRITE_OID_FIELD(tsmcost);
WRITE_NODE_FIELD(repeatable);
WRITE_NODE_FIELD(args);
}
static void
_outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
{
@ -2594,6 +2566,16 @@ _outRangeTblFunction(StringInfo str, const RangeTblFunction *node)
WRITE_BITMAPSET_FIELD(funcparams);
}
static void
_outTableSampleClause(StringInfo str, const TableSampleClause *node)
{
WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
WRITE_OID_FIELD(tsmhandler);
WRITE_NODE_FIELD(args);
WRITE_NODE_FIELD(repeatable);
}
static void
_outAExpr(StringInfo str, const A_Expr *node)
{
@ -2845,6 +2827,18 @@ _outRangeFunction(StringInfo str, const RangeFunction *node)
WRITE_NODE_FIELD(coldeflist);
}
static void
_outRangeTableSample(StringInfo str, const RangeTableSample *node)
{
WRITE_NODE_TYPE("RANGETABLESAMPLE");
WRITE_NODE_FIELD(relation);
WRITE_NODE_FIELD(method);
WRITE_NODE_FIELD(args);
WRITE_NODE_FIELD(repeatable);
WRITE_LOCATION_FIELD(location);
}
static void
_outConstraint(StringInfo str, const Constraint *node)
{
@ -3002,6 +2996,9 @@ _outNode(StringInfo str, const void *obj)
case T_SeqScan:
_outSeqScan(str, obj);
break;
case T_SampleScan:
_outSampleScan(str, obj);
break;
case T_IndexScan:
_outIndexScan(str, obj);
break;
@ -3038,9 +3035,6 @@ _outNode(StringInfo str, const void *obj)
case T_CustomScan:
_outCustomScan(str, obj);
break;
case T_SampleScan:
_outSampleScan(str, obj);
break;
case T_Join:
_outJoin(str, obj);
break;
@ -3393,12 +3387,6 @@ _outNode(StringInfo str, const void *obj)
case T_CommonTableExpr:
_outCommonTableExpr(str, obj);
break;
case T_RangeTableSample:
_outRangeTableSample(str, obj);
break;
case T_TableSampleClause:
_outTableSampleClause(str, obj);
break;
case T_SetOperationStmt:
_outSetOperationStmt(str, obj);
break;
@ -3408,6 +3396,9 @@ _outNode(StringInfo str, const void *obj)
case T_RangeTblFunction:
_outRangeTblFunction(str, obj);
break;
case T_TableSampleClause:
_outTableSampleClause(str, obj);
break;
case T_A_Expr:
_outAExpr(str, obj);
break;
@ -3450,6 +3441,9 @@ _outNode(StringInfo str, const void *obj)
case T_RangeFunction:
_outRangeFunction(str, obj);
break;
case T_RangeTableSample:
_outRangeTableSample(str, obj);
break;
case T_Constraint:
_outConstraint(str, obj);
break;

61
src/backend/nodes/readfuncs.c
View File

@ -367,46 +367,6 @@ _readCommonTableExpr(void)
READ_DONE();
}
/*
* _readRangeTableSample
*/
static RangeTableSample *
_readRangeTableSample(void)
{
READ_LOCALS(RangeTableSample);
READ_NODE_FIELD(relation);
READ_STRING_FIELD(method);
READ_NODE_FIELD(repeatable);
READ_NODE_FIELD(args);
READ_DONE();
}
/*
* _readTableSampleClause
*/
static TableSampleClause *
_readTableSampleClause(void)
{
READ_LOCALS(TableSampleClause);
READ_OID_FIELD(tsmid);
READ_BOOL_FIELD(tsmseqscan);
READ_BOOL_FIELD(tsmpagemode);
READ_OID_FIELD(tsminit);
READ_OID_FIELD(tsmnextblock);
READ_OID_FIELD(tsmnexttuple);
READ_OID_FIELD(tsmexaminetuple);
READ_OID_FIELD(tsmend);
READ_OID_FIELD(tsmreset);
READ_OID_FIELD(tsmcost);
READ_NODE_FIELD(repeatable);
READ_NODE_FIELD(args);
READ_DONE();
}
/*
* _readSetOperationStmt
*/
@ -1391,6 +1351,21 @@ _readRangeTblFunction(void)
READ_DONE();
}
/*
* _readTableSampleClause
*/
static TableSampleClause *
_readTableSampleClause(void)
{
READ_LOCALS(TableSampleClause);
READ_OID_FIELD(tsmhandler);
READ_NODE_FIELD(args);
READ_NODE_FIELD(repeatable);
READ_DONE();
}
/*
* parseNodeString
@ -1426,10 +1401,6 @@ parseNodeString(void)
return_value = _readRowMarkClause();
else if (MATCH("COMMONTABLEEXPR", 15))
return_value = _readCommonTableExpr();
else if (MATCH("RANGETABLESAMPLE", 16))
return_value = _readRangeTableSample();
else if (MATCH("TABLESAMPLECLAUSE", 17))
return_value = _readTableSampleClause();
else if (MATCH("SETOPERATIONSTMT", 16))
return_value = _readSetOperationStmt();
else if (MATCH("ALIAS", 5))
@ -1528,6 +1499,8 @@ parseNodeString(void)
return_value = _readRangeTblEntry();
else if (MATCH("RANGETBLFUNCTION", 16))
return_value = _readRangeTblFunction();
else if (MATCH("TABLESAMPLECLAUSE", 17))
return_value = _readTableSampleClause();
else if (MATCH("NOTIFY", 6))
return_value = _readNotifyStmt();
else if (MATCH("DECLARECURSOR", 13))

100
src/backend/optimizer/path/allpaths.c
View File

@ -18,6 +18,7 @@
#include <math.h>
#include "access/sysattr.h"
#include "access/tsmapi.h"
#include "catalog/pg_class.h"
#include "catalog/pg_operator.h"
#include "foreign/fdwapi.h"
@ -390,7 +391,7 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
}
else if (rte->tablesample != NULL)
{
/* Build sample scan on relation */
/* Sampled relation */
set_tablesample_rel_pathlist(root, rel, rte);
}
else
@ -480,11 +481,40 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
/*
* set_tablesample_rel_size
* Set size estimates for a sampled relation.
* Set size estimates for a sampled relation
*/
static void
set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
TableSampleClause *tsc = rte->tablesample;
TsmRoutine *tsm;
BlockNumber pages;
double tuples;
/*
* Test any partial indexes of rel for applicability. We must do this
* first since partial unique indexes can affect size estimates.
*/
check_partial_indexes(root, rel);
/*
* Call the sampling method's estimation function to estimate the number
* of pages it will read and the number of tuples it will return. (Note:
* we assume the function returns sane values.)
*/
tsm = GetTsmRoutine(tsc->tsmhandler);
tsm->SampleScanGetSampleSize(root, rel, tsc->args,
&pages, &tuples);
/*
* For the moment, because we will only consider a SampleScan path for the
* rel, it's okay to just overwrite the pages and tuples estimates for the
* whole relation. If we ever consider multiple path types for sampled
* rels, we'll need more complication.
*/
rel->pages = pages;
rel->tuples = tuples;
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
}
@ -492,8 +522,6 @@ set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
/*
* set_tablesample_rel_pathlist
* Build access paths for a sampled relation
*
* There is only one possible path - sampling scan
*/
static void
set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
@ -502,15 +530,41 @@ set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *
Path *path;
/*
* We don't support pushing join clauses into the quals of a seqscan, but
* it could still have required parameterization due to LATERAL refs in
* its tlist.
* We don't support pushing join clauses into the quals of a samplescan,
* but it could still have required parameterization due to LATERAL refs
* in its tlist or TABLESAMPLE arguments.
*/
required_outer = rel->lateral_relids;
/* We only do sample scan if it was requested */
/* Consider sampled scan */
path = create_samplescan_path(root, rel, required_outer);
rel->pathlist = list_make1(path);
/*
* If the sampling method does not support repeatable scans, we must avoid
* plans that would scan the rel multiple times. Ideally, we'd simply
* avoid putting the rel on the inside of a nestloop join; but adding such
* a consideration to the planner seems like a great deal of complication
* to support an uncommon usage of second-rate sampling methods. Instead,
* if there is a risk that the query might perform an unsafe join, just
* wrap the SampleScan in a Materialize node. We can check for joins by
* counting the membership of all_baserels (note that this correctly
* counts inheritance trees as single rels). If we're inside a subquery,
* we can't easily check whether a join might occur in the outer query, so
* just assume one is possible.
*
* GetTsmRoutine is relatively expensive compared to the other tests here,
* so check repeatable_across_scans last, even though that's a bit odd.
*/
if ((root->query_level > 1 ||
bms_membership(root->all_baserels) != BMS_SINGLETON) &&
!(GetTsmRoutine(rte->tablesample->tsmhandler)->repeatable_across_scans))
{
path = (Path *) create_material_path(rel, path);
}
add_path(rel, path);
/* For the moment, at least, there are no other paths to consider */
}
/*
@ -2450,7 +2504,33 @@ print_path(PlannerInfo *root, Path *path, int indent)
switch (nodeTag(path))
{
case T_Path:
ptype = "SeqScan";
switch (path->pathtype)
{
case T_SeqScan:
ptype = "SeqScan";
break;
case T_SampleScan:
ptype = "SampleScan";
break;
case T_SubqueryScan:
ptype = "SubqueryScan";
break;
case T_FunctionScan:
ptype = "FunctionScan";
break;
case T_ValuesScan:
ptype = "ValuesScan";
break;
case T_CteScan:
ptype = "CteScan";
break;
case T_WorkTableScan:
ptype = "WorkTableScan";
break;
default:
ptype = "???Path";
break;
}
break;
case T_IndexPath:
ptype = "IdxScan";

57
src/backend/optimizer/path/costsize.c
View File

@ -74,6 +74,7 @@
#include <math.h>
#include "access/htup_details.h"
#include "access/tsmapi.h"
#include "executor/executor.h"
#include "executor/nodeHash.h"
#include "miscadmin.h"
@ -223,64 +224,66 @@ cost_seqscan(Path *path, PlannerInfo *root,
* cost_samplescan
* Determines and returns the cost of scanning a relation using sampling.
*
* From planner/optimizer perspective, we don't care all that much about cost
* itself since there is always only one scan path to consider when sampling
* scan is present, but number of rows estimation is still important.
*
* 'baserel' is the relation to be scanned
* 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
*/
void
cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
cost_samplescan(Path *path, PlannerInfo *root,
RelOptInfo *baserel, ParamPathInfo *param_info)
{
Cost startup_cost = 0;
Cost run_cost = 0;
RangeTblEntry *rte;
TableSampleClause *tsc;
TsmRoutine *tsm;
double spc_seq_page_cost,
spc_random_page_cost,
spc_page_cost;
QualCost qpqual_cost;
Cost cpu_per_tuple;
BlockNumber pages;
double tuples;
RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
TableSampleClause *tablesample = rte->tablesample;
/* Should only be applied to base relations */
/* Should only be applied to base relations with tablesample clauses */
Assert(baserel->relid > 0);
Assert(baserel->rtekind == RTE_RELATION);
rte = planner_rt_fetch(baserel->relid, root);
Assert(rte->rtekind == RTE_RELATION);
tsc = rte->tablesample;
Assert(tsc != NULL);
tsm = GetTsmRoutine(tsc->tsmhandler);
/* Mark the path with the correct row estimate */
if (path->param_info)
path->rows = path->param_info->ppi_rows;
if (param_info)
path->rows = param_info->ppi_rows;
else
path->rows = baserel->rows;
/* Call the sampling method's costing function. */
OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
PointerGetDatum(path), PointerGetDatum(baserel),
PointerGetDatum(tablesample->args),
PointerGetDatum(&pages), PointerGetDatum(&tuples));
/* fetch estimated page cost for tablespace containing table */
get_tablespace_page_costs(baserel->reltablespace,
&spc_random_page_cost,
&spc_seq_page_cost);
spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
spc_random_page_cost;
/* if NextSampleBlock is used, assume random access, else sequential */
spc_page_cost = (tsm->NextSampleBlock != NULL) ?
spc_random_page_cost : spc_seq_page_cost;
/*
* disk costs
* disk costs (recall that baserel->pages has already been set to the
* number of pages the sampling method will visit)
*/
run_cost += spc_page_cost * pages;
run_cost += spc_page_cost * baserel->pages;
/* CPU costs */
get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
/*
* CPU costs (recall that baserel->tuples has already been set to the
* number of tuples the sampling method will select). Note that we ignore
* execution cost of the TABLESAMPLE parameter expressions; they will be
* evaluated only once per scan, and in most usages they'll likely be
* simple constants anyway. We also don't charge anything for the
* calculations the sampling method might do internally.
*/
get_restriction_qual_cost(root, baserel, param_info, &qpqual_cost);
startup_cost += qpqual_cost.startup;
cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
run_cost += cpu_per_tuple * tuples;
run_cost += cpu_per_tuple * baserel->tuples;
path->startup_cost = startup_cost;
path->total_cost = startup_cost + run_cost;

34
src/backend/optimizer/plan/createplan.c
View File

@ -102,7 +102,8 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
static void copy_path_costsize(Plan *dest, Path *src);
static void copy_plan_costsize(Plan *dest, Plan *src);
static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid,
TableSampleClause *tsc);
static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
Oid indexid, List *indexqual, List *indexqualorig,
List *indexorderby, List *indexorderbyorig,
@ -1148,7 +1149,7 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
/*
* create_samplescan_plan
* Returns a samplecan plan for the base relation scanned by 'best_path'
* Returns a samplescan plan for the base relation scanned by 'best_path'
* with restriction clauses 'scan_clauses' and targetlist 'tlist'.
*/
static SampleScan *
@ -1157,11 +1158,15 @@ create_samplescan_plan(PlannerInfo *root, Path *best_path,
{
SampleScan *scan_plan;
Index scan_relid = best_path->parent->relid;
RangeTblEntry *rte;
TableSampleClause *tsc;
/* it should be a base rel with tablesample clause... */
/* it should be a base rel with a tablesample clause... */
Assert(scan_relid > 0);
Assert(best_path->parent->rtekind == RTE_RELATION);
Assert(best_path->pathtype == T_SampleScan);
rte = planner_rt_fetch(scan_relid, root);
Assert(rte->rtekind == RTE_RELATION);
tsc = rte->tablesample;
Assert(tsc != NULL);
/* Sort clauses into best execution order */
scan_clauses = order_qual_clauses(root, scan_clauses);
@ -1174,13 +1179,16 @@ create_samplescan_plan(PlannerInfo *root, Path *best_path,
{
scan_clauses = (List *)
replace_nestloop_params(root, (Node *) scan_clauses);
tsc = (TableSampleClause *)
replace_nestloop_params(root, (Node *) tsc);
}
scan_plan = make_samplescan(tlist,
scan_clauses,
scan_relid);
scan_relid,
tsc);
copy_path_costsize(&scan_plan->plan, best_path);
copy_path_costsize(&scan_plan->scan.plan, best_path);
return scan_plan;
}
@ -2161,9 +2169,9 @@ create_customscan_plan(PlannerInfo *root, CustomPath *best_path,
ListCell *lc;
/* Recursively transform child paths. */
foreach (lc, best_path->custom_paths)
foreach(lc, best_path->custom_paths)
{
Plan *plan = create_plan_recurse(root, (Path *) lfirst(lc));
Plan *plan = create_plan_recurse(root, (Path *) lfirst(lc));
custom_plans = lappend(custom_plans, plan);
}
@ -3437,17 +3445,19 @@ make_seqscan(List *qptlist,
static SampleScan *
make_samplescan(List *qptlist,
List *qpqual,
Index scanrelid)
Index scanrelid,
TableSampleClause *tsc)
{
SampleScan *node = makeNode(SampleScan);
Plan *plan = &node->plan;
Plan *plan = &node->scan.plan;
/* cost should be inserted by caller */
plan->targetlist = qptlist;
plan->qual = qpqual;
plan->lefttree = NULL;
plan->righttree = NULL;
node->scanrelid = scanrelid;
node->scan.scanrelid = scanrelid;
node->tablesample = tsc;
return node;
}

4
src/backend/optimizer/plan/initsplan.c
View File

@ -306,7 +306,9 @@ extract_lateral_references(PlannerInfo *root, RelOptInfo *brel, Index rtindex)
return;
/* Fetch the appropriate variables */
if (rte->rtekind == RTE_SUBQUERY)
if (rte->rtekind == RTE_RELATION)
vars = pull_vars_of_level((Node *) rte->tablesample, 0);
else if (rte->rtekind == RTE_SUBQUERY)
vars = pull_vars_of_level((Node *) rte->subquery, 1);
else if (rte->rtekind == RTE_FUNCTION)
vars = pull_vars_of_level((Node *) rte->functions, 0);

19
src/backend/optimizer/plan/planner.c
View File

@ -505,14 +505,10 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
if (rte->rtekind == RTE_RELATION)
{
if (rte->tablesample)
{
rte->tablesample->args = (List *)
preprocess_expression(root, (Node *) rte->tablesample->args,
rte->tablesample = (TableSampleClause *)
preprocess_expression(root,
(Node *) rte->tablesample,
EXPRKIND_TABLESAMPLE);
rte->tablesample->repeatable = (Node *)
preprocess_expression(root, rte->tablesample->repeatable,
EXPRKIND_TABLESAMPLE);
}
}
else if (rte->rtekind == RTE_SUBQUERY)
{
@ -697,11 +693,14 @@ preprocess_expression(PlannerInfo *root, Node *expr, int kind)
* If the query has any join RTEs, replace join alias variables with
* base-relation variables. We must do this before sublink processing,
* else sublinks expanded out from join aliases would not get processed.
* We can skip it in non-lateral RTE functions and VALUES lists, however,
* since they can't contain any Vars of the current query level.
* We can skip it in non-lateral RTE functions, VALUES lists, and
* TABLESAMPLE clauses, however, since they can't contain any Vars of the
* current query level.
*/
if (root->hasJoinRTEs &&
!(kind == EXPRKIND_RTFUNC || kind == EXPRKIND_VALUES))
!(kind == EXPRKIND_RTFUNC ||
kind == EXPRKIND_VALUES ||
kind == EXPRKIND_TABLESAMPLE))
expr = flatten_join_alias_vars(root, expr);
/*

18
src/backend/optimizer/plan/setrefs.c
View File

@ -372,9 +372,8 @@ flatten_rtes_walker(Node *node, PlannerGlobal *glob)
*
* In the flat rangetable, we zero out substructure pointers that are not
* needed by the executor; this reduces the storage space and copying cost
* for cached plans. We keep only the tablesample field (which we'd otherwise
* have to put in the plan tree, anyway); the ctename, alias and eref Alias
* fields, which are needed by EXPLAIN; and the selectedCols, insertedCols and
* for cached plans. We keep only the ctename, alias and eref Alias fields,
* which are needed by EXPLAIN, and the selectedCols, insertedCols and
* updatedCols bitmaps, which are needed for executor-startup permissions
* checking and for trigger event checking.
*/
@ -388,6 +387,7 @@ add_rte_to_flat_rtable(PlannerGlobal *glob, RangeTblEntry *rte)
memcpy(newrte, rte, sizeof(RangeTblEntry));
/* zap unneeded sub-structure */
newrte->tablesample = NULL;
newrte->subquery = NULL;
newrte->joinaliasvars = NIL;
newrte->functions = NIL;
@ -456,11 +456,13 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
{
SampleScan *splan = (SampleScan *) plan;
splan->scanrelid += rtoffset;
splan->plan.targetlist =
fix_scan_list(root, splan->plan.targetlist, rtoffset);
splan->plan.qual =
fix_scan_list(root, splan->plan.qual, rtoffset);
splan->scan.scanrelid += rtoffset;
splan->scan.plan.targetlist =
fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
splan->scan.plan.qual =
fix_scan_list(root, splan->scan.plan.qual, rtoffset);
splan->tablesample = (TableSampleClause *)
fix_scan_expr(root, (Node *) splan->tablesample, rtoffset);
}
break;
case T_IndexScan:

7
src/backend/optimizer/plan/subselect.c
View File

@ -2216,7 +2216,12 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
break;
case T_SeqScan:
context.paramids = bms_add_members(context.paramids, scan_params);
break;
case T_SampleScan:
finalize_primnode((Node *) ((SampleScan *) plan)->tablesample,
&context);
context.paramids = bms_add_members(context.paramids, scan_params);
break;
@ -2384,7 +2389,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
bms_add_members(context.paramids, scan_params);
/* child nodes if any */
foreach (lc, cscan->custom_plans)
foreach(lc, cscan->custom_plans)
{
context.paramids =
bms_add_members(context.paramids,

13
src/backend/optimizer/prep/prepjointree.c
View File

@ -1091,12 +1091,15 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
switch (child_rte->rtekind)
{
case RTE_RELATION:
if (child_rte->tablesample)
child_rte->lateral = true;
break;
case RTE_SUBQUERY:
case RTE_FUNCTION:
case RTE_VALUES:
child_rte->lateral = true;
break;
case RTE_RELATION:
case RTE_JOIN:
case RTE_CTE:
/* these can't contain any lateral references */
@ -1909,6 +1912,13 @@ replace_vars_in_jointree(Node *jtnode,
{
switch (rte->rtekind)
{
case RTE_RELATION:
/* shouldn't be marked LATERAL unless tablesample */
Assert(rte->tablesample);
rte->tablesample = (TableSampleClause *)
pullup_replace_vars((Node *) rte->tablesample,
context);
break;
case RTE_SUBQUERY:
rte->subquery =
pullup_replace_vars_subquery(rte->subquery,
@ -1924,7 +1934,6 @@ replace_vars_in_jointree(Node *jtnode,
pullup_replace_vars((Node *) rte->values_lists,
context);
break;
case RTE_RELATION:
case RTE_JOIN:
case RTE_CTE:
/* these shouldn't be marked LATERAL */

8
src/backend/optimizer/util/pathnode.c
View File

@ -713,7 +713,7 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
/*
* create_samplescan_path
* Like seqscan but uses sampling function while scanning.
* Creates a path node for a sampled table scan.
*/
Path *
create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
@ -726,7 +726,7 @@ create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer
required_outer);
pathnode->pathkeys = NIL; /* samplescan has unordered result */
cost_samplescan(pathnode, root, rel);
cost_samplescan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
@ -1773,6 +1773,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
{
case T_SeqScan:
return create_seqscan_path(root, rel, required_outer);
case T_SampleScan:
return (Path *) create_samplescan_path(root, rel, required_outer);
case T_IndexScan:
case T_IndexOnlyScan:
{
@ -1805,8 +1807,6 @@ reparameterize_path(PlannerInfo *root, Path *path,
case T_SubqueryScan:
return create_subqueryscan_path(root, rel, path->pathkeys,
required_outer);
case T_SampleScan:
return (Path *) create_samplescan_path(root, rel, required_outer);
default:
break;
}

27
src/backend/parser/gram.y
View File

@ -457,8 +457,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <jexpr> joined_table
%type <range> relation_expr
%type <range> relation_expr_opt_alias
%type <node> tablesample_clause opt_repeatable_clause
%type <target> target_el single_set_clause set_target insert_column_item
%type <node> relation_expr_tablesample tablesample_clause opt_repeatable_clause
%type <str> generic_option_name
%type <node> generic_option_arg
@ -10491,9 +10491,13 @@ table_ref: relation_expr opt_alias_clause
$1->alias = $2;
$$ = (Node *) $1;
}
| relation_expr_tablesample
| relation_expr opt_alias_clause tablesample_clause
{
$$ = (Node *) $1;
RangeTableSample *n = (RangeTableSample *) $3;
$1->alias = $2;
/* relation_expr goes inside the RangeTableSample node */
n->relation = (Node *) $1;
$$ = (Node *) n;
}
| func_table func_alias_clause
{
@ -10820,23 +10824,18 @@ relation_expr_opt_alias: relation_expr %prec UMINUS
}
;
relation_expr_tablesample: relation_expr opt_alias_clause tablesample_clause
{
RangeTableSample *n = (RangeTableSample *) $3;
n->relation = $1;
n->relation->alias = $2;
$$ = (Node *) n;
}
;
/*
* TABLESAMPLE decoration in a FROM item
*/
tablesample_clause:
TABLESAMPLE ColId '(' expr_list ')' opt_repeatable_clause
TABLESAMPLE func_name '(' expr_list ')' opt_repeatable_clause
{
RangeTableSample *n = makeNode(RangeTableSample);
/* n->relation will be filled in later */
n->method = $2;
n->args = $4;
n->repeatable = $6;
n->location = @2;
$$ = (Node *) n;
}
;

190
src/backend/parser/parse_clause.c
View File

@ -18,8 +18,8 @@
#include "miscadmin.h"
#include "access/heapam.h"
#include "access/tsmapi.h"
#include "catalog/catalog.h"
#include "access/htup_details.h"
#include "catalog/heap.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_type.h"
@ -43,7 +43,7 @@
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
/* Convenience macro for the most common makeNamespaceItem() case */
#define makeDefaultNSItem(rte) makeNamespaceItem(rte, true, true, false, true)
@ -63,6 +63,8 @@ static RangeTblEntry *transformRangeSubselect(ParseState *pstate,
RangeSubselect *r);
static RangeTblEntry *transformRangeFunction(ParseState *pstate,
RangeFunction *r);
static TableSampleClause *transformRangeTableSample(ParseState *pstate,
RangeTableSample *rts);
static Node *transformFromClauseItem(ParseState *pstate, Node *n,
RangeTblEntry **top_rte, int *top_rti,
List **namespace);
@ -423,40 +425,6 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
return result;
}
static RangeTblEntry *
transformTableSampleEntry(ParseState *pstate, RangeTableSample *rv)
{
RangeTblEntry *rte = NULL;
CommonTableExpr *cte = NULL;
TableSampleClause *tablesample = NULL;
/* if relation has an unqualified name, it might be a CTE reference */
if (!rv->relation->schemaname)
{
Index levelsup;
cte = scanNameSpaceForCTE(pstate, rv->relation->relname, &levelsup);
}
/* We first need to build a range table entry */
if (!cte)
rte = transformTableEntry(pstate, rv->relation);
if (!rte ||
(rte->relkind != RELKIND_RELATION &&
rte->relkind != RELKIND_MATVIEW))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
parser_errposition(pstate, rv->relation->location)));
tablesample = ParseTableSample(pstate, rv->method, rv->repeatable,
rv->args, rv->relation->location);
rte->tablesample = tablesample;
return rte;
}
/*
* transformTableEntry --- transform a RangeVar (simple relation reference)
*/
@ -748,6 +716,109 @@ transformRangeFunction(ParseState *pstate, RangeFunction *r)
return rte;
}
/*
* transformRangeTableSample --- transform a TABLESAMPLE clause
*
* Caller has already transformed rts->relation, we just have to validate
* the remaining fields and create a TableSampleClause node.
*/
static TableSampleClause *
transformRangeTableSample(ParseState *pstate, RangeTableSample *rts)
{
TableSampleClause *tablesample;
Oid handlerOid;
Oid funcargtypes[1];
TsmRoutine *tsm;
List *fargs;
ListCell *larg,
*ltyp;
/*
* To validate the sample method name, look up the handler function, which
* has the same name, one dummy INTERNAL argument, and a result type of
* tsm_handler. (Note: tablesample method names are not schema-qualified
* in the SQL standard; but since they are just functions to us, we allow
* schema qualification to resolve any potential ambiguity.)
*/
funcargtypes[0] = INTERNALOID;
handlerOid = LookupFuncName(rts->method, 1, funcargtypes, true);
/* we want error to complain about no-such-method, not no-such-function */
if (!OidIsValid(handlerOid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("tablesample method %s does not exist",
NameListToString(rts->method)),
parser_errposition(pstate, rts->location)));
/* check that handler has correct return type */
if (get_func_rettype(handlerOid) != TSM_HANDLEROID)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("function %s must return type \"tsm_handler\"",
NameListToString(rts->method)),
parser_errposition(pstate, rts->location)));
/* OK, run the handler to get TsmRoutine, for argument type info */
tsm = GetTsmRoutine(handlerOid);
tablesample = makeNode(TableSampleClause);
tablesample->tsmhandler = handlerOid;
/* check user provided the expected number of arguments */
if (list_length(rts->args) != list_length(tsm->parameterTypes))
ereport(ERROR,
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
errmsg_plural("tablesample method %s requires %d argument, not %d",
"tablesample method %s requires %d arguments, not %d",
list_length(tsm->parameterTypes),
NameListToString(rts->method),
list_length(tsm->parameterTypes),
list_length(rts->args)),
parser_errposition(pstate, rts->location)));
/*
* Transform the arguments, typecasting them as needed. Note we must also
* assign collations now, because assign_query_collations() doesn't
* examine any substructure of RTEs.
*/
fargs = NIL;
forboth(larg, rts->args, ltyp, tsm->parameterTypes)
{
Node *arg = (Node *) lfirst(larg);
Oid argtype = lfirst_oid(ltyp);
arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
arg = coerce_to_specific_type(pstate, arg, argtype, "TABLESAMPLE");
assign_expr_collations(pstate, arg);
fargs = lappend(fargs, arg);
}
tablesample->args = fargs;
/* Process REPEATABLE (seed) */
if (rts->repeatable != NULL)
{
Node *arg;
if (!tsm->repeatable_across_queries)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("tablesample method %s does not support REPEATABLE",
NameListToString(rts->method)),
parser_errposition(pstate, rts->location)));
arg = transformExpr(pstate, rts->repeatable, EXPR_KIND_FROM_FUNCTION);
arg = coerce_to_specific_type(pstate, arg, FLOAT8OID, "REPEATABLE");
assign_expr_collations(pstate, arg);
tablesample->repeatable = (Expr *) arg;
}
else
tablesample->repeatable = NULL;
return tablesample;
}
/*
* transformFromClauseItem -
@ -844,6 +915,33 @@ transformFromClauseItem(ParseState *pstate, Node *n,
rtr->rtindex = rtindex;
return (Node *) rtr;
}
else if (IsA(n, RangeTableSample))
{
/* TABLESAMPLE clause (wrapping some other valid FROM node) */
RangeTableSample *rts = (RangeTableSample *) n;
Node *rel;
RangeTblRef *rtr;
RangeTblEntry *rte;
/* Recursively transform the contained relation */
rel = transformFromClauseItem(pstate, rts->relation,
top_rte, top_rti, namespace);
/* Currently, grammar could only return a RangeVar as contained rel */
Assert(IsA(rel, RangeTblRef));
rtr = (RangeTblRef *) rel;
rte = rt_fetch(rtr->rtindex, pstate->p_rtable);
/* We only support this on plain relations and matviews */
if (rte->relkind != RELKIND_RELATION &&
rte->relkind != RELKIND_MATVIEW)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("TABLESAMPLE clause can only be applied to tables and materialized views"),
parser_errposition(pstate, exprLocation(rts->relation))));
/* Transform TABLESAMPLE details and attach to the RTE */
rte->tablesample = transformRangeTableSample(pstate, rts);
return (Node *) rtr;
}
else if (IsA(n, JoinExpr))
{
/* A newfangled join expression */
@ -1165,26 +1263,6 @@ transformFromClauseItem(ParseState *pstate, Node *n,
return (Node *) j;
}
else if (IsA(n, RangeTableSample))
{
/* Tablesample reference */
RangeTableSample *rv = (RangeTableSample *) n;
RangeTblRef *rtr;
RangeTblEntry *rte = NULL;
int rtindex;
rte = transformTableSampleEntry(pstate, rv);
/* assume new rte is at end */
rtindex = list_length(pstate->p_rtable);
Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
*top_rte = rte;
*top_rti = rtindex;
*namespace = list_make1(makeDefaultNSItem(rte));
rtr = makeNode(RangeTblRef);
rtr->rtindex = rtindex;
return (Node *) rtr;
}
else
elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
return NULL; /* can't get here, keep compiler quiet */

144
src/backend/parser/parse_func.c
View File

@ -18,7 +18,6 @@
#include "catalog/pg_aggregate.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "catalog/pg_tablesample_method.h"
#include "funcapi.h"
#include "lib/stringinfo.h"
#include "nodes/makefuncs.h"
@ -27,7 +26,6 @@
#include "parser/parse_clause.h"
#include "parser/parse_coerce.h"
#include "parser/parse_func.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_type.h"
@ -769,148 +767,6 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
}
/*
* ParseTableSample
*
* Parse TABLESAMPLE clause and process the arguments
*/
TableSampleClause *
ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
List *sampleargs, int location)
{
HeapTuple tuple;
Form_pg_tablesample_method tsm;
Form_pg_proc procform;
TableSampleClause *tablesample;
List *fargs;
ListCell *larg;
int nargs,
initnargs;
Oid init_arg_types[FUNC_MAX_ARGS];
/* Load the tablesample method */
tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
if (!HeapTupleIsValid(tuple))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("tablesample method \"%s\" does not exist",
samplemethod),
parser_errposition(pstate, location)));
tablesample = makeNode(TableSampleClause);
tablesample->tsmid = HeapTupleGetOid(tuple);
tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
tablesample->tsmseqscan = tsm->tsmseqscan;
tablesample->tsmpagemode = tsm->tsmpagemode;
tablesample->tsminit = tsm->tsminit;
tablesample->tsmnextblock = tsm->tsmnextblock;
tablesample->tsmnexttuple = tsm->tsmnexttuple;
tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
tablesample->tsmend = tsm->tsmend;
tablesample->tsmreset = tsm->tsmreset;
tablesample->tsmcost = tsm->tsmcost;
ReleaseSysCache(tuple);
/* Validate the parameters against init function definition. */
tuple = SearchSysCache1(PROCOID,
ObjectIdGetDatum(tablesample->tsminit));
if (!HeapTupleIsValid(tuple)) /* should not happen */
elog(ERROR, "cache lookup failed for function %u",
tablesample->tsminit);
procform = (Form_pg_proc) GETSTRUCT(tuple);
initnargs = procform->pronargs;
Assert(initnargs >= 3);
/*
* First parameter is used to pass the SampleScanState, second is seed
* (REPEATABLE), skip the processing for them here, just assert that the
* types are correct.
*/
Assert(procform->proargtypes.values[0] == INTERNALOID);
Assert(procform->proargtypes.values[1] == INT4OID);
initnargs -= 2;
memcpy(init_arg_types, procform->proargtypes.values + 2,
initnargs * sizeof(Oid));
/* Now we are done with the catalog */
ReleaseSysCache(tuple);
/* Process repeatable (seed) */
if (repeatable != NULL)
{
Node *arg = repeatable;
if (arg && IsA(arg, A_Const))
{
A_Const *con = (A_Const *) arg;
if (con->val.type == T_Null)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("REPEATABLE clause must be NOT NULL numeric value"),
parser_errposition(pstate, con->location)));
}
arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
tablesample->repeatable = arg;
}
else
tablesample->repeatable = NULL;
/* Check user provided expected number of arguments. */
if (list_length(sampleargs) != initnargs)
ereport(ERROR,
(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
errmsg_plural("tablesample method \"%s\" expects %d argument got %d",
"tablesample method \"%s\" expects %d arguments got %d",
initnargs,
samplemethod,
initnargs, list_length(sampleargs)),
parser_errposition(pstate, location)));
/* Transform the arguments, typecasting them as needed. */
fargs = NIL;
nargs = 0;
foreach(larg, sampleargs)
{
Node *inarg = (Node *) lfirst(larg);
Node *arg = transformExpr(pstate, inarg, EXPR_KIND_FROM_FUNCTION);
Oid argtype = exprType(arg);
if (argtype != init_arg_types[nargs])
{
if (!can_coerce_type(1, &argtype, &init_arg_types[nargs],
COERCION_IMPLICIT))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("wrong parameter %d for tablesample method \"%s\"",
nargs + 1, samplemethod),
errdetail("Expected type %s got %s.",
format_type_be(init_arg_types[nargs]),
format_type_be(argtype)),
parser_errposition(pstate, exprLocation(inarg))));
arg = coerce_type(pstate, arg, argtype, init_arg_types[nargs], -1,
COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
}
fargs = lappend(fargs, arg);
nargs++;
}
/* Pass the arguments down */
tablesample->args = fargs;
return tablesample;
}
/* func_match_argtypes()
*
* Given a list of candidate functions (having the right name and number

4
src/backend/rewrite/rewriteHandler.c
View File

@ -418,6 +418,10 @@ rewriteRuleAction(Query *parsetree,
switch (rte->rtekind)
{
case RTE_RELATION:
sub_action->hasSubLinks =
checkExprHasSubLink((Node *) rte->tablesample);
break;
case RTE_FUNCTION:
sub_action->hasSubLinks =
checkExprHasSubLink((Node *) rte->functions);

27
src/backend/utils/adt/pseudotypes.c
View File

@ -373,6 +373,33 @@ fdw_handler_out(PG_FUNCTION_ARGS)
}
/*
* tsm_handler_in - input routine for pseudo-type TSM_HANDLER.
*/
Datum
tsm_handler_in(PG_FUNCTION_ARGS)
{
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot accept a value of type tsm_handler")));
PG_RETURN_VOID(); /* keep compiler quiet */
}
/*
* tsm_handler_out - output routine for pseudo-type TSM_HANDLER.
*/
Datum
tsm_handler_out(PG_FUNCTION_ARGS)
{
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot display a value of type tsm_handler")));
PG_RETURN_VOID(); /* keep compiler quiet */
}
/*
* internal_in - input routine for pseudo-type INTERNAL.
*/

94
src/backend/utils/adt/ruleutils.c
View File

@ -32,7 +32,6 @@
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_tablesample_method.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
@ -349,8 +348,6 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
int prettyFlags);
static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
int prettyFlags, int wrapColumn);
static void get_tablesample_def(TableSampleClause *tablesample,
deparse_context *context);
static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
TupleDesc resultDesc,
int prettyFlags, int wrapColumn, int startIndent);
@ -416,6 +413,8 @@ static void get_column_alias_list(deparse_columns *colinfo,
static void get_from_clause_coldeflist(RangeTblFunction *rtfunc,
deparse_columns *colinfo,
deparse_context *context);
static void get_tablesample_def(TableSampleClause *tablesample,
deparse_context *context);
static void get_opclass_name(Oid opclass, Oid actual_datatype,
StringInfo buf);
static Node *processIndirection(Node *node, deparse_context *context,
@ -4235,50 +4234,6 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
heap_close(ev_relation, AccessShareLock);
}
/* ----------
* get_tablesample_def - Convert TableSampleClause back to SQL
* ----------
*/
static void
get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
{
StringInfo buf = context->buf;
HeapTuple tuple;
Form_pg_tablesample_method tsm;
char *tsmname;
int nargs;
ListCell *l;
/* Load the tablesample method */
tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
if (!HeapTupleIsValid(tuple))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("cache lookup failed for tablesample method %u",
tablesample->tsmid)));
tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
tsmname = NameStr(tsm->tsmname);
appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
ReleaseSysCache(tuple);
nargs = 0;
foreach(l, tablesample->args)
{
if (nargs++ > 0)
appendStringInfoString(buf, ", ");
get_rule_expr((Node *) lfirst(l), context, true);
}
appendStringInfoChar(buf, ')');
if (tablesample->repeatable != NULL)
{
appendStringInfoString(buf, " REPEATABLE (");
get_rule_expr(tablesample->repeatable, context, true);
appendStringInfoChar(buf, ')');
}
}
/* ----------
* get_query_def - Parse back one query parsetree
@ -8781,9 +8736,6 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
only_marker(rte),
generate_relation_name(rte->relid,
context->namespaces));
if (rte->tablesample)
get_tablesample_def(rte->tablesample, context);
break;
case RTE_SUBQUERY:
/* Subquery RTE */
@ -8963,6 +8915,10 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
/* Else print column aliases as needed */
get_column_alias_list(colinfo, context);
}
/* Tablesample clause must go after any alias */
if (rte->rtekind == RTE_RELATION && rte->tablesample)
get_tablesample_def(rte->tablesample, context);
}
else if (IsA(jtnode, JoinExpr))
{
@ -9162,6 +9118,44 @@ get_from_clause_coldeflist(RangeTblFunction *rtfunc,
appendStringInfoChar(buf, ')');
}
/*
* get_tablesample_def - print a TableSampleClause
*/
static void
get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
{
StringInfo buf = context->buf;
Oid argtypes[1];
int nargs;
ListCell *l;
/*
* We should qualify the handler's function name if it wouldn't be
* resolved by lookup in the current search path.
*/
argtypes[0] = INTERNALOID;
appendStringInfo(buf, " TABLESAMPLE %s (",
generate_function_name(tablesample->tsmhandler, 1,
NIL, argtypes,
false, NULL, EXPR_KIND_NONE));
nargs = 0;
foreach(l, tablesample->args)
{
if (nargs++ > 0)
appendStringInfoString(buf, ", ");
get_rule_expr((Node *) lfirst(l), context, false);
}
appendStringInfoChar(buf, ')');
if (tablesample->repeatable != NULL)
{
appendStringInfoString(buf, " REPEATABLE (");
get_rule_expr((Node *) tablesample->repeatable, context, false);
appendStringInfoChar(buf, ')');
}
}
/*
* get_opclass_name - fetch name of an index operator class
*

27
src/backend/utils/cache/lsyscache.c vendored
View File

@ -32,7 +32,6 @@
#include "catalog/pg_range.h"
#include "catalog/pg_statistic.h"
#include "catalog/pg_transform.h"
#include "catalog/pg_tablesample_method.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
@ -2997,29 +2996,3 @@ get_range_subtype(Oid rangeOid)
else
return InvalidOid;
}
/* ---------- PG_TABLESAMPLE_METHOD CACHE ---------- */
/*
* get_tablesample_method_name - given a tablesample method OID,
* look up the name or NULL if not found
*/
char *
get_tablesample_method_name(Oid tsmid)
{
HeapTuple tuple;
tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmid));
if (HeapTupleIsValid(tuple))
{
Form_pg_tablesample_method tup =
(Form_pg_tablesample_method) GETSTRUCT(tuple);
char *result;
result = pstrdup(NameStr(tup->tsmname));
ReleaseSysCache(tuple);
return result;
}
else
return NULL;
}

23
src/backend/utils/cache/syscache.c vendored
View File

@ -56,7 +56,6 @@
#include "catalog/pg_shseclabel.h"
#include "catalog/pg_replication_origin.h"
#include "catalog/pg_statistic.h"
#include "catalog/pg_tablesample_method.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_transform.h"
#include "catalog/pg_ts_config.h"
@ -667,28 +666,6 @@ static const struct cachedesc cacheinfo[] = {
},
128
},
{TableSampleMethodRelationId, /* TABLESAMPLEMETHODNAME */
TableSampleMethodNameIndexId,
1,
{
Anum_pg_tablesample_method_tsmname,
0,
0,
0,
},
2
},
{TableSampleMethodRelationId, /* TABLESAMPLEMETHODOID */
TableSampleMethodOidIndexId,
1,
{
ObjectIdAttributeNumber,
0,
0,
0,
},
2
},
{TableSpaceRelationId, /* TABLESPACEOID */
TablespaceOidIndexId,
1,

2
src/backend/utils/errcodes.txt
View File

@ -177,6 +177,8 @@ Section: Class 22 - Data Exception
2201B E ERRCODE_INVALID_REGULAR_EXPRESSION invalid_regular_expression
2201W E ERRCODE_INVALID_ROW_COUNT_IN_LIMIT_CLAUSE invalid_row_count_in_limit_clause
2201X E ERRCODE_INVALID_ROW_COUNT_IN_RESULT_OFFSET_CLAUSE invalid_row_count_in_result_offset_clause
2202H E ERRCODE_INVALID_TABLESAMPLE_ARGUMENT invalid_tablesample_argument
2202G E ERRCODE_INVALID_TABLESAMPLE_REPEAT invalid_tablesample_repeat
22009 E ERRCODE_INVALID_TIME_ZONE_DISPLACEMENT_VALUE invalid_time_zone_displacement_value
2200C E ERRCODE_INVALID_USE_OF_ESCAPE_CHARACTER invalid_use_of_escape_character
2200G E ERRCODE_MOST_SPECIFIC_TYPE_MISMATCH most_specific_type_mismatch

2
src/backend/utils/misc/sampling.c
View File

@ -228,7 +228,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
void
sampler_random_init_state(long seed, SamplerRandomState randstate)
{
randstate[0] = RAND48_SEED_0;
randstate[0] = 0x330e; /* same as pg_erand48, but could be anything */
randstate[1] = (unsigned short) seed;
randstate[2] = (unsigned short) (seed >> 16);
}

10
src/bin/psql/tab-complete.c
View File

@ -738,13 +738,15 @@ static const SchemaQuery Query_for_list_of_matviews = {
" WHERE substring(pg_catalog.quote_ident(evtname),1,%d)='%s'"
#define Query_for_list_of_tablesample_methods \
" SELECT pg_catalog.quote_ident(tsmname) "\
" FROM pg_catalog.pg_tablesample_method "\
" WHERE substring(pg_catalog.quote_ident(tsmname),1,%d)='%s'"
" SELECT pg_catalog.quote_ident(proname) "\
" FROM pg_catalog.pg_proc "\
" WHERE prorettype = 'pg_catalog.tsm_handler'::pg_catalog.regtype AND "\
" proargtypes[0] = 'pg_catalog.internal'::pg_catalog.regtype AND "\
" substring(pg_catalog.quote_ident(proname),1,%d)='%s'"
#define Query_for_list_of_policies \
" SELECT pg_catalog.quote_ident(polname) "\
" FROM pg_catalog.pg_policy " \
" FROM pg_catalog.pg_policy "\
" WHERE substring(pg_catalog.quote_ident(polname),1,%d)='%s'"
#define Query_for_list_of_tables_for_policy \

4
src/include/access/heapam.h
View File

@ -116,11 +116,13 @@ extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key);
extern HeapScanDesc heap_beginscan_sampling(Relation relation,
Snapshot snapshot, int nkeys, ScanKey key,
bool allow_strat, bool allow_pagemode);
bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
BlockNumber endBlk);
extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
extern void heap_rescan(HeapScanDesc scan, ScanKey key);
extern void heap_rescan_set_params(HeapScanDesc scan, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_endscan(HeapScanDesc scan);
extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);

61
src/include/access/tablesample.h
View File

@ -1,61 +0,0 @@
/*-------------------------------------------------------------------------
*
* tablesample.h
* Public header file for TABLESAMPLE clause interface
*
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/tablesample.h
*
*-------------------------------------------------------------------------
*/
#ifndef TABLESAMPLE_H
#define TABLESAMPLE_H
#include "access/relscan.h"
#include "executor/executor.h"
typedef struct TableSampleDesc
{
HeapScanDesc heapScan;
TupleDesc tupDesc; /* Mostly useful for tsmexaminetuple */
void *tsmdata; /* private method data */
/* These point to he function of the TABLESAMPLE Method. */
FmgrInfo tsminit;
FmgrInfo tsmnextblock;
FmgrInfo tsmnexttuple;
FmgrInfo tsmexaminetuple;
FmgrInfo tsmreset;
FmgrInfo tsmend;
} TableSampleDesc;
extern TableSampleDesc *tablesample_init(SampleScanState *scanstate,
TableSampleClause *tablesample);
extern HeapTuple tablesample_getnext(TableSampleDesc *desc);
extern void tablesample_reset(TableSampleDesc *desc);
extern void tablesample_end(TableSampleDesc *desc);
extern HeapTuple tablesample_source_getnext(TableSampleDesc *desc);
extern HeapTuple tablesample_source_gettup(TableSampleDesc *desc, ItemPointer tid,
bool *visible);
extern Datum tsm_system_init(PG_FUNCTION_ARGS);
extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
extern Datum tsm_system_end(PG_FUNCTION_ARGS);
extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
#endif

81
src/include/access/tsmapi.h Normal file
View File

@ -0,0 +1,81 @@
/*-------------------------------------------------------------------------
*
* tsmapi.h
* API for tablesample methods
*
* Copyright (c) 2015, PostgreSQL Global Development Group
*
* src/include/access/tsmapi.h
*
*-------------------------------------------------------------------------
*/
#ifndef TSMAPI_H
#define TSMAPI_H
#include "nodes/execnodes.h"
#include "nodes/relation.h"
/*
* Callback function signatures --- see tablesample-method.sgml for more info.
*/
typedef void (*SampleScanGetSampleSize_function) (PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
typedef void (*InitSampleScan_function) (SampleScanState *node,
int eflags);
typedef void (*BeginSampleScan_function) (SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
typedef BlockNumber (*NextSampleBlock_function) (SampleScanState *node);
typedef OffsetNumber (*NextSampleTuple_function) (SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
typedef void (*EndSampleScan_function) (SampleScanState *node);
/*
* TsmRoutine is the struct returned by a tablesample method's handler
* function. It provides pointers to the callback functions needed by the
* planner and executor, as well as additional information about the method.
*
* More function pointers are likely to be added in the future.
* Therefore it's recommended that the handler initialize the struct with
* makeNode(TsmRoutine) so that all fields are set to NULL. This will
* ensure that no fields are accidentally left undefined.
*/
typedef struct TsmRoutine
{
NodeTag type;
/* List of datatype OIDs for the arguments of the TABLESAMPLE clause */
List *parameterTypes;
/* Can method produce repeatable samples across, or even within, queries? */
bool repeatable_across_queries;
bool repeatable_across_scans;
/* Functions for planning a SampleScan on a physical table */
SampleScanGetSampleSize_function SampleScanGetSampleSize;
/* Functions for executing a SampleScan on a physical table */
InitSampleScan_function InitSampleScan; /* can be NULL */
BeginSampleScan_function BeginSampleScan;
NextSampleBlock_function NextSampleBlock; /* can be NULL */
NextSampleTuple_function NextSampleTuple;
EndSampleScan_function EndSampleScan; /* can be NULL */
} TsmRoutine;
/* Functions in access/tablesample/tablesample.c */
extern TsmRoutine *GetTsmRoutine(Oid tsmhandler);
#endif /* TSMAPI_H */

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201507171
#define CATALOG_VERSION_NO 201507252
#endif

5
src/include/catalog/indexing.h
View File

@ -316,11 +316,6 @@ DECLARE_UNIQUE_INDEX(pg_replication_origin_roiident_index, 6001, on pg_replicati
DECLARE_UNIQUE_INDEX(pg_replication_origin_roname_index, 6002, on pg_replication_origin using btree(roname text_pattern_ops));
#define ReplicationOriginNameIndex 6002
DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3331, on pg_tablesample_method using btree(tsmname name_ops));
#define TableSampleMethodNameIndexId 3331
DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3332, on pg_tablesample_method using btree(oid oid_ops));
#define TableSampleMethodOidIndexId 3332
/* last step of initialization script: build the indexes declared above */
BUILD_INDICES

37
src/include/catalog/pg_proc.h
View File

@ -3734,6 +3734,16 @@ DATA(insert OID = 3116 ( fdw_handler_in PGNSP PGUID 12 1 0 0 0 f f f f f f i 1
DESCR("I/O");
DATA(insert OID = 3117 ( fdw_handler_out PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2275 "3115" _null_ _null_ _null_ _null_ _null_ fdw_handler_out _null_ _null_ _null_ ));
DESCR("I/O");
DATA(insert OID = 3311 ( tsm_handler_in PGNSP PGUID 12 1 0 0 0 f f f f f f i 1 0 3310 "2275" _null_ _null_ _null_ _null_ _null_ tsm_handler_in _null_ _null_ _null_ ));
DESCR("I/O");
DATA(insert OID = 3312 ( tsm_handler_out PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2275 "3310" _null_ _null_ _null_ _null_ _null_ tsm_handler_out _null_ _null_ _null_ ));
DESCR("I/O");
/* tablesample method handlers */
DATA(insert OID = 3313 ( bernoulli PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 3310 "2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_handler _null_ _null_ _null_ ));
DESCR("BERNOULLI tablesample method handler");
DATA(insert OID = 3314 ( system PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 3310 "2281" _null_ _null_ _null_ _null_ _null_ tsm_system_handler _null_ _null_ _null_ ));
DESCR("SYSTEM tablesample method handler");
/* cryptographic */
DATA(insert OID = 2311 ( md5 PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "25" _null_ _null_ _null_ _null_ _null_ md5_text _null_ _null_ _null_ ));
@ -5321,33 +5331,6 @@ DESCR("get an individual replication origin's replication progress");
DATA(insert OID = 6014 ( pg_show_replication_origin_status PGNSP PGUID 12 1 100 0 0 f f f f f t v 0 0 2249 "" "{26,25,3220,3220}" "{o,o,o,o}" "{local_id, external_id, remote_lsn, local_lsn}" _null_ _null_ pg_show_replication_origin_status _null_ _null_ _null_ ));
DESCR("get progress for all replication origins");
/* tablesample */
DATA(insert OID = 3335 ( tsm_system_init PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_ _null_ tsm_system_init _null_ _null_ _null_ ));
DESCR("tsm_system_init(internal)");
DATA(insert OID = 3336 ( tsm_system_nextblock PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_ _null_ tsm_system_nextblock _null_ _null_ _null_ ));
DESCR("tsm_system_nextblock(internal)");
DATA(insert OID = 3337 ( tsm_system_nexttuple PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_ _null_ tsm_system_nexttuple _null_ _null_ _null_ ));
DESCR("tsm_system_nexttuple(internal)");
DATA(insert OID = 3338 ( tsm_system_end PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_system_end _null_ _null_ _null_ ));
DESCR("tsm_system_end(internal)");
DATA(insert OID = 3339 ( tsm_system_reset PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_system_reset _null_ _null_ _null_ ));
DESCR("tsm_system_reset(internal)");
DATA(insert OID = 3340 ( tsm_system_cost PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ _null_ tsm_system_cost _null_ _null_ _null_ ));
DESCR("tsm_system_cost(internal)");
DATA(insert OID = 3341 ( tsm_bernoulli_init PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_init _null_ _null_ _null_ ));
DESCR("tsm_bernoulli_init(internal)");
DATA(insert OID = 3342 ( tsm_bernoulli_nextblock PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_nextblock _null_ _null_ _null_ ));
DESCR("tsm_bernoulli_nextblock(internal)");
DATA(insert OID = 3343 ( tsm_bernoulli_nexttuple PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
DESCR("tsm_bernoulli_nexttuple(internal)");
DATA(insert OID = 3344 ( tsm_bernoulli_end PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_end _null_ _null_ _null_ ));
DESCR("tsm_bernoulli_end(internal)");
DATA(insert OID = 3345 ( tsm_bernoulli_reset PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_reset _null_ _null_ _null_ ));
DESCR("tsm_bernoulli_reset(internal)");
DATA(insert OID = 3346 ( tsm_bernoulli_cost PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_cost _null_ _null_ _null_ ));
DESCR("tsm_bernoulli_cost(internal)");
/*
* Symbolic values for provolatile column: these indicate whether the result
* of a function is dependent *only* on the values of its explicit arguments,

81
src/include/catalog/pg_tablesample_method.h
View File

@ -1,81 +0,0 @@
/*-------------------------------------------------------------------------
*
* pg_tablesample_method.h
* definition of the table scan methods.
*
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/catalog/pg_tablesample_method.h
*
*
*-------------------------------------------------------------------------
*/
#ifndef PG_TABLESAMPLE_METHOD_H
#define PG_TABLESAMPLE_METHOD_H
#include "catalog/genbki.h"
#include "catalog/objectaddress.h"
/* ----------------
* pg_tablesample_method definition. cpp turns this into
* typedef struct FormData_pg_tablesample_method
* ----------------
*/
#define TableSampleMethodRelationId 3330
CATALOG(pg_tablesample_method,3330)
{
NameData tsmname; /* tablesample method name */
bool tsmseqscan; /* does this method scan whole table
* sequentially? */
bool tsmpagemode; /* does this method scan page at a time? */
regproc tsminit; /* init scan function */
regproc tsmnextblock; /* function returning next block to sample or
* InvalidBlockOffset if finished */
regproc tsmnexttuple; /* function returning next tuple offset from
* current block or InvalidOffsetNumber if end
* of the block was reacher */
regproc tsmexaminetuple;/* optional function which can examine tuple
* contents and decide if tuple should be
* returned or not */
regproc tsmend; /* end scan function */
regproc tsmreset; /* reset state - used by rescan */
regproc tsmcost; /* costing function */
} FormData_pg_tablesample_method;
/* ----------------
* Form_pg_tablesample_method corresponds to a pointer to a tuple with
* the format of pg_tablesample_method relation.
* ----------------
*/
typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
/* ----------------
* compiler constants for pg_tablesample_method
* ----------------
*/
#define Natts_pg_tablesample_method 10
#define Anum_pg_tablesample_method_tsmname 1
#define Anum_pg_tablesample_method_tsmseqscan 2
#define Anum_pg_tablesample_method_tsmpagemode 3
#define Anum_pg_tablesample_method_tsminit 4
#define Anum_pg_tablesample_method_tsmnextblock 5
#define Anum_pg_tablesample_method_tsmnexttuple 6
#define Anum_pg_tablesample_method_tsmexaminetuple 7
#define Anum_pg_tablesample_method_tsmend 8
#define Anum_pg_tablesample_method_tsmreset 9
#define Anum_pg_tablesample_method_tsmcost 10
/* ----------------
* initial contents of pg_tablesample_method
* ----------------
*/
DATA(insert OID = 3333 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
DESCR("SYSTEM table sampling method");
DATA(insert OID = 3334 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
DESCR("BERNOULLI table sampling method");
#endif /* PG_TABLESAMPLE_METHOD_H */

2
src/include/catalog/pg_type.h
View File

@ -694,6 +694,8 @@ DATA(insert OID = 3500 ( anyenum PGNSP PGUID 4 t p P f t \054 0 0 0 anyenum_in
#define ANYENUMOID 3500
DATA(insert OID = 3115 ( fdw_handler PGNSP PGUID 4 t p P f t \054 0 0 0 fdw_handler_in fdw_handler_out - - - - - i p f 0 -1 0 0 _null_ _null_ _null_ ));
#define FDW_HANDLEROID 3115
DATA(insert OID = 3310 ( tsm_handler PGNSP PGUID 4 t p P f t \054 0 0 0 tsm_handler_in tsm_handler_out - - - - - i p f 0 -1 0 0 _null_ _null_ _null_ ));
#define TSM_HANDLEROID 3310
DATA(insert OID = 3831 ( anyrange PGNSP PGUID -1 f p P f t \054 0 0 0 anyrange_in anyrange_out - - - - - d x f 0 -1 0 0 _null_ _null_ _null_ ));
#define ANYRANGEOID 3831

2
src/include/executor/nodeSamplescan.h
View File

@ -4,7 +4,7 @@
*
*
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/executor/nodeSamplescan.h

15
src/include/nodes/execnodes.h
View File

@ -1257,13 +1257,22 @@ typedef struct ScanState
*/
typedef ScanState SeqScanState;
/*
* SampleScan
/* ----------------
* SampleScanState information
* ----------------
*/
typedef struct SampleScanState
{
ScanState ss;
struct TableSampleDesc *tsdesc;
List *args; /* expr states for TABLESAMPLE params */
ExprState *repeatable; /* expr state for REPEATABLE expr */
/* use struct pointer to avoid including tsmapi.h here */
struct TsmRoutine *tsmroutine; /* descriptor for tablesample method */
void *tsm_state; /* tablesample method can keep state here */
bool use_bulkread; /* use bulkread buffer access strategy? */
bool use_pagemode; /* use page-at-a-time visibility checking? */
bool begun; /* false means need to call BeginSampleScan */
uint32 seed; /* random seed */
} SampleScanState;
/*

9
src/include/nodes/nodes.h
View File

@ -51,6 +51,7 @@ typedef enum NodeTag
T_BitmapOr,
T_Scan,
T_SeqScan,
T_SampleScan,
T_IndexScan,
T_IndexOnlyScan,
T_BitmapIndexScan,
@ -61,7 +62,6 @@ typedef enum NodeTag
T_ValuesScan,
T_CteScan,
T_WorkTableScan,
T_SampleScan,
T_ForeignScan,
T_CustomScan,
T_Join,
@ -400,6 +400,7 @@ typedef enum NodeTag
T_WindowDef,
T_RangeSubselect,
T_RangeFunction,
T_RangeTableSample,
T_TypeName,
T_ColumnDef,
T_IndexElem,
@ -407,6 +408,7 @@ typedef enum NodeTag
T_DefElem,
T_RangeTblEntry,
T_RangeTblFunction,
T_TableSampleClause,
T_WithCheckOption,
T_SortGroupClause,
T_GroupingSet,
@ -425,8 +427,6 @@ typedef enum NodeTag
T_OnConflictClause,
T_CommonTableExpr,
T_RoleSpec,
T_RangeTableSample,
T_TableSampleClause,
/*
* TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
@ -452,7 +452,8 @@ typedef enum NodeTag
T_WindowObjectData, /* private in nodeWindowAgg.c */
T_TIDBitmap, /* in nodes/tidbitmap.h */
T_InlineCodeBlock, /* in nodes/parsenodes.h */
T_FdwRoutine /* in foreign/fdwapi.h */
T_FdwRoutine, /* in foreign/fdwapi.h */
T_TsmRoutine /* in access/tsmapi.h */
} NodeTag;
/*

59
src/include/nodes/parsenodes.h
View File

@ -337,26 +337,6 @@ typedef struct FuncCall
int location; /* token location, or -1 if unknown */
} FuncCall;
/*
* TableSampleClause - a sampling method information
*/
typedef struct TableSampleClause
{
NodeTag type;
Oid tsmid;
bool tsmseqscan;
bool tsmpagemode;
Oid tsminit;
Oid tsmnextblock;
Oid tsmnexttuple;
Oid tsmexaminetuple;
Oid tsmend;
Oid tsmreset;
Oid tsmcost;
Node *repeatable;
List *args;
} TableSampleClause;
/*
* A_Star - '*' representing all columns of a table or compound field
*
@ -558,19 +538,23 @@ typedef struct RangeFunction
} RangeFunction;
/*
* RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
* RangeTableSample - TABLESAMPLE appearing in a raw FROM clause
*
* SQL Standard specifies only one parameter which is percentage. But we allow
* custom tablesample methods which may need different input arguments so we
* accept list of arguments.
* This node, appearing only in raw parse trees, represents
* <relation> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
* Currently, the <relation> can only be a RangeVar, but we might in future
* allow RangeSubselect and other options. Note that the RangeTableSample
* is wrapped around the node representing the <relation>, rather than being
* a subfield of it.
*/
typedef struct RangeTableSample
{
NodeTag type;
RangeVar *relation;
char *method; /* sampling method */
Node *repeatable;
List *args; /* arguments for sampling method */
Node *relation; /* relation to be sampled */
List *method; /* sampling method name (possibly qualified) */
List *args; /* argument(s) for sampling method */
Node *repeatable; /* REPEATABLE expression, or NULL if none */
int location; /* method name location, or -1 if unknown */
} RangeTableSample;
/*
@ -810,7 +794,7 @@ typedef struct RangeTblEntry
*/
Oid relid; /* OID of the relation */
char relkind; /* relation kind (see pg_class.relkind) */
TableSampleClause *tablesample; /* sampling method and parameters */
struct TableSampleClause *tablesample; /* sampling info, or NULL */
/*
* Fields valid for a subquery RTE (else NULL):
@ -912,6 +896,19 @@ typedef struct RangeTblFunction
Bitmapset *funcparams; /* PARAM_EXEC Param IDs affecting this func */
} RangeTblFunction;
/*
* TableSampleClause - TABLESAMPLE appearing in a transformed FROM clause
*
* Unlike RangeTableSample, this is a subnode of the relevant RangeTblEntry.
*/
typedef struct TableSampleClause
{
NodeTag type;
Oid tsmhandler; /* OID of the tablesample handler function */
List *args; /* tablesample argument expression(s) */
Expr *repeatable; /* REPEATABLE expression, or NULL if none */
} TableSampleClause;
/*
* WithCheckOption -
* representation of WITH CHECK OPTION checks to be applied to new tuples
@ -2520,7 +2517,7 @@ typedef struct RenameStmt
typedef struct AlterObjectSchemaStmt
{
NodeTag type;
ObjectType objectType; /* OBJECT_TABLE, OBJECT_TYPE, etc */
ObjectType objectType; /* OBJECT_TABLE, OBJECT_TYPE, etc */
RangeVar *relation; /* in case it's a table */
List *object; /* in case it's some other object */
List *objarg; /* argument types, if applicable */
@ -2535,7 +2532,7 @@ typedef struct AlterObjectSchemaStmt
typedef struct AlterOwnerStmt
{
NodeTag type;
ObjectType objectType; /* OBJECT_TABLE, OBJECT_TYPE, etc */
ObjectType objectType; /* OBJECT_TABLE, OBJECT_TYPE, etc */
RangeVar *relation; /* in case it's a table */
List *object; /* in case it's some other object */
List *objarg; /* argument types, if applicable */

7
src/include/nodes/plannodes.h
View File

@ -287,7 +287,12 @@ typedef Scan SeqScan;
* table sample scan node
* ----------------
*/
typedef Scan SampleScan;
typedef struct SampleScan
{
Scan scan;
/* use struct pointer to avoid including parsenodes.h here */
struct TableSampleClause *tablesample;
} SampleScan;
/* ----------------
* index scan node

3
src/include/optimizer/cost.h
View File

@ -68,7 +68,8 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
double index_pages, PlannerInfo *root);
extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
ParamPathInfo *param_info);
extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
ParamPathInfo *param_info);
extern void cost_index(IndexPath *path, PlannerInfo *root,
double loop_count);
extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,

5
src/include/parser/parse_func.h
View File

@ -33,11 +33,6 @@ typedef enum
extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
FuncCall *fn, int location);
extern TableSampleClause *ParseTableSample(ParseState *pstate,
char *samplemethod,
Node *repeatable, List *args,
int location);
extern FuncDetailCode func_get_detail(List *funcname,
List *fargs, List *fargnames,
int nargs, Oid *argtypes,

4
src/include/port.h
View File

@ -357,10 +357,6 @@ extern off_t ftello(FILE *stream);
#endif
#endif
#define RAND48_SEED_0 (0x330e)
#define RAND48_SEED_1 (0xabcd)
#define RAND48_SEED_2 (0x1234)
extern double pg_erand48(unsigned short xseed[3]);
extern long pg_lrand48(void);
extern void pg_srand48(long seed);

8
src/include/utils/builtins.h
View File

@ -566,6 +566,8 @@ extern Datum language_handler_in(PG_FUNCTION_ARGS);
extern Datum language_handler_out(PG_FUNCTION_ARGS);
extern Datum fdw_handler_in(PG_FUNCTION_ARGS);
extern Datum fdw_handler_out(PG_FUNCTION_ARGS);
extern Datum tsm_handler_in(PG_FUNCTION_ARGS);
extern Datum tsm_handler_out(PG_FUNCTION_ARGS);
extern Datum internal_in(PG_FUNCTION_ARGS);
extern Datum internal_out(PG_FUNCTION_ARGS);
extern Datum opaque_in(PG_FUNCTION_ARGS);
@ -1213,6 +1215,12 @@ extern Datum ginqueryarrayextract(PG_FUNCTION_ARGS);
extern Datum ginarrayconsistent(PG_FUNCTION_ARGS);
extern Datum ginarraytriconsistent(PG_FUNCTION_ARGS);
/* access/tablesample/bernoulli.c */
extern Datum tsm_bernoulli_handler(PG_FUNCTION_ARGS);
/* access/tablesample/system.c */
extern Datum tsm_system_handler(PG_FUNCTION_ARGS);
/* access/transam/twophase.c */
extern Datum pg_prepared_xact(PG_FUNCTION_ARGS);

1
src/include/utils/lsyscache.h
View File

@ -156,7 +156,6 @@ extern void free_attstatsslot(Oid atttype,
extern char *get_namespace_name(Oid nspid);
extern char *get_namespace_name_or_temp(Oid nspid);
extern Oid get_range_subtype(Oid rangeOid);
extern char *get_tablesample_method_name(Oid tsmid);
#define type_is_array(typid) (get_element_type(typid) != InvalidOid)
/* type_is_array_domain accepts both plain arrays and domains over arrays */

2
src/include/utils/syscache.h
View File

@ -81,8 +81,6 @@ enum SysCacheIdentifier
REPLORIGNAME,
RULERELNAME,
STATRELATTINH,
TABLESAMPLEMETHODNAME,
TABLESAMPLEMETHODOID,
TABLESPACEOID,
TRFOID,
TRFTYPELANG,

3
src/port/erand48.c
View File

@ -33,6 +33,9 @@
#include <math.h>
#define RAND48_SEED_0 (0x330e)
#define RAND48_SEED_1 (0xabcd)
#define RAND48_SEED_2 (0x1234)
#define RAND48_MULT_0 (0xe66d)
#define RAND48_MULT_1 (0xdeec)
#define RAND48_MULT_2 (0x0005)

24
src/test/regress/expected/rowsecurity.out
View File

@ -101,15 +101,17 @@ NOTICE: f_leak => great manga
44 | 8 | 1 | rls_regress_user2 | great manga | manga
(4 rows)
SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
NOTICE: f_leak => my first novel
-- try a sampled version
SELECT * FROM document TABLESAMPLE BERNOULLI(50) REPEATABLE(0)
WHERE f_leak(dtitle) ORDER BY did;
NOTICE: f_leak => my first manga
NOTICE: f_leak => great science fiction
NOTICE: f_leak => great manga
did | cid | dlevel | dauthor | dtitle
-----+-----+--------+-------------------+-----------------------
1 | 11 | 1 | rls_regress_user1 | my first novel
4 | 44 | 1 | rls_regress_user1 | my first manga
6 | 22 | 1 | rls_regress_user2 | great science fiction
8 | 44 | 1 | rls_regress_user2 | great manga
(3 rows)
-- viewpoint from rls_regress_user2
@ -156,20 +158,20 @@ NOTICE: f_leak => great manga
44 | 8 | 1 | rls_regress_user2 | great manga | manga
(8 rows)
SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
NOTICE: f_leak => my first novel
NOTICE: f_leak => my second novel
-- try a sampled version
SELECT * FROM document TABLESAMPLE BERNOULLI(50) REPEATABLE(0)
WHERE f_leak(dtitle) ORDER BY did;
NOTICE: f_leak => my first manga
NOTICE: f_leak => my second manga
NOTICE: f_leak => great science fiction
NOTICE: f_leak => great technology book
NOTICE: f_leak => great manga
did | cid | dlevel | dauthor | dtitle
-----+-----+--------+-------------------+-----------------------
1 | 11 | 1 | rls_regress_user1 | my first novel
2 | 11 | 2 | rls_regress_user1 | my second novel
4 | 44 | 1 | rls_regress_user1 | my first manga
5 | 44 | 2 | rls_regress_user1 | my second manga
6 | 22 | 1 | rls_regress_user2 | great science fiction
7 | 33 | 2 | rls_regress_user2 | great technology book
(5 rows)
8 | 44 | 1 | rls_regress_user2 | great manga
(4 rows)
EXPLAIN (COSTS OFF) SELECT * FROM document WHERE f_leak(dtitle);
QUERY PLAN

4
src/test/regress/expected/rules.out
View File

@ -2202,6 +2202,10 @@ street| SELECT r.name,
FROM ONLY road r,
real_city c
WHERE (c.outline ## r.thepath);
test_tablesample_v1| SELECT test_tablesample.id
FROM test_tablesample TABLESAMPLE system ((10 * 2)) REPEATABLE (2);
test_tablesample_v2| SELECT test_tablesample.id
FROM test_tablesample TABLESAMPLE system (99);
toyemp| SELECT emp.name,
emp.age,
emp.location,

1
src/test/regress/expected/sanity_check.out
View File

@ -128,7 +128,6 @@ pg_shdepend|t
pg_shdescription|t
pg_shseclabel|t
pg_statistic|t
pg_tablesample_method|t
pg_tablespace|t
pg_transform|t
pg_trigger|t

304
src/test/regress/expected/tablesample.out
View File

@ -1,107 +1,123 @@
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10);
-- use fillfactor so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample
SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i);
SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
id
----
0
1
2
3
4
5
9
(7 rows)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
id
----
6
7
8
(3 rows)
(6 rows)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
id
----
(0 rows)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
id
----
3
4
5
6
7
8
(6 rows)
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (0);
id
----
4
5
6
7
8
(5 rows)
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (0);
id
----
7
(1 row)
-- 100% should give repeatable count results (ie, all rows) in any case
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
count
-------
10
(1 row)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
id
----
0
1
2
6
7
8
9
(7 rows)
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
id
----
0
1
3
4
5
(5 rows)
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
id
----
0
5
(2 rows)
CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
pg_get_viewdef
--------------------------------------------------------------------------------
SELECT test_tablesample.id +
FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (1+2);
count
-------
10
(1 row)
SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
pg_get_viewdef
-----------------------------------------------------------
SELECT test_tablesample.id +
FROM test_tablesample TABLESAMPLE system ((99)::real);
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (0.4);
count
-------
10
(1 row)
CREATE VIEW test_tablesample_v1 AS
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
CREATE VIEW test_tablesample_v2 AS
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
\d+ test_tablesample_v1
View "public.test_tablesample_v1"
Column | Type | Modifiers | Storage | Description
--------+---------+-----------+---------+-------------
id | integer | | plain |
View definition:
SELECT test_tablesample.id
FROM test_tablesample TABLESAMPLE system ((10 * 2)) REPEATABLE (2);
\d+ test_tablesample_v2
View "public.test_tablesample_v2"
Column | Type | Modifiers | Storage | Description
--------+---------+-----------+---------+-------------
id | integer | | plain |
View definition:
SELECT test_tablesample.id
FROM test_tablesample TABLESAMPLE system (99);
-- check a sampled query doesn't affect cursor in progress
BEGIN;
DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
DECLARE tablesample_cur CURSOR FOR
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
FETCH FIRST FROM tablesample_cur;
id
----
0
3
(1 row)
FETCH NEXT FROM tablesample_cur;
id
----
1
4
(1 row)
FETCH NEXT FROM tablesample_cur;
id
----
2
5
(1 row)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
id
----
0
1
2
3
4
5
9
(7 rows)
6
7
8
(6 rows)
FETCH NEXT FROM tablesample_cur;
id
@ -124,19 +140,19 @@ FETCH NEXT FROM tablesample_cur;
FETCH FIRST FROM tablesample_cur;
id
----
0
3
(1 row)
FETCH NEXT FROM tablesample_cur;
id
----
1
4
(1 row)
FETCH NEXT FROM tablesample_cur;
id
----
2
5
(1 row)
FETCH NEXT FROM tablesample_cur;
@ -159,41 +175,129 @@ FETCH NEXT FROM tablesample_cur;
CLOSE tablesample_cur;
END;
EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
QUERY PLAN
-------------------------------------------------------------------------------
Sample Scan (system) on test_tablesample (cost=0.00..26.35 rows=635 width=4)
EXPLAIN (COSTS OFF)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (2);
QUERY PLAN
--------------------------------------------------------------------
Sample Scan on test_tablesample
Sampling: system ('50'::real) REPEATABLE ('2'::double precision)
(2 rows)
EXPLAIN (COSTS OFF)
SELECT * FROM test_tablesample_v1;
QUERY PLAN
--------------------------------------------------------------------
Sample Scan on test_tablesample
Sampling: system ('20'::real) REPEATABLE ('2'::double precision)
(2 rows)
-- check inheritance behavior
explain (costs off)
select count(*) from person tablesample bernoulli (100);
QUERY PLAN
-------------------------------------------------
Aggregate
-> Append
-> Sample Scan on person
Sampling: bernoulli ('100'::real)
-> Sample Scan on emp
Sampling: bernoulli ('100'::real)
-> Sample Scan on student
Sampling: bernoulli ('100'::real)
-> Sample Scan on stud_emp
Sampling: bernoulli ('100'::real)
(10 rows)
select count(*) from person tablesample bernoulli (100);
count
-------
58
(1 row)
EXPLAIN SELECT * FROM test_tablesample_v1;
QUERY PLAN
-------------------------------------------------------------------------------
Sample Scan (system) on test_tablesample (cost=0.00..10.54 rows=254 width=4)
select count(*) from person;
count
-------
58
(1 row)
-- check that collations get assigned within the tablesample arguments
SELECT count(*) FROM test_tablesample TABLESAMPLE bernoulli (('1'::text < '0'::text)::int);
count
-------
0
(1 row)
-- check behavior during rescans, as well as correct handling of min/max pct
select * from
(values (0),(100)) v(pct),
lateral (select count(*) from tenk1 tablesample bernoulli (pct)) ss;
pct | count
-----+-------
0 | 0
100 | 10000
(2 rows)
select * from
(values (0),(100)) v(pct),
lateral (select count(*) from tenk1 tablesample system (pct)) ss;
pct | count
-----+-------
0 | 0
100 | 10000
(2 rows)
explain (costs off)
select pct, count(unique1) from
(values (0),(100)) v(pct),
lateral (select * from tenk1 tablesample bernoulli (pct)) ss
group by pct;
QUERY PLAN
--------------------------------------------------------
HashAggregate
Group Key: "*VALUES*".column1
-> Nested Loop
-> Values Scan on "*VALUES*"
-> Sample Scan on tenk1
Sampling: bernoulli ("*VALUES*".column1)
(6 rows)
select pct, count(unique1) from
(values (0),(100)) v(pct),
lateral (select * from tenk1 tablesample bernoulli (pct)) ss
group by pct;
pct | count
-----+-------
100 | 10000
(1 row)
select pct, count(unique1) from
(values (0),(100)) v(pct),
lateral (select * from tenk1 tablesample system (pct)) ss
group by pct;
pct | count
-----+-------
100 | 10000
(1 row)
-- errors
SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
ERROR: tablesample method "foobar" does not exist
ERROR: tablesample method foobar does not exist
LINE 1: SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
^
^
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (NULL);
ERROR: TABLESAMPLE parameter cannot be null
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
ERROR: REPEATABLE clause must be NOT NULL numeric value
LINE 1: ... test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
^
ERROR: TABLESAMPLE REPEATABLE parameter cannot be null
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
ERROR: invalid sample size
HINT: Sample size must be numeric value between 0 and 100 (inclusive).
ERROR: sample percentage must be between 0 and 100
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
ERROR: invalid sample size
HINT: Sample size must be numeric value between 0 and 100 (inclusive).
ERROR: sample percentage must be between 0 and 100
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
ERROR: invalid sample size
HINT: Sample size must be numeric value between 0 and 100 (inclusive).
ERROR: sample percentage must be between 0 and 100
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
ERROR: invalid sample size
HINT: Sample size must be numeric value between 0 and 100 (inclusive).
ERROR: sample percentage must be between 0 and 100
SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
ERROR: TABLESAMPLE clause can only be used on tables and materialized views
ERROR: TABLESAMPLE clause can only be applied to tables and materialized views
LINE 1: SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1)...
^
INSERT INTO test_tablesample_v1 VALUES(1);
@ -202,30 +306,10 @@ DETAIL: Views containing TABLESAMPLE are not automatically updatable.
HINT: To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.
WITH query_select AS (SELECT * FROM test_tablesample)
SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
ERROR: TABLESAMPLE clause can only be used on tables and materialized views
ERROR: TABLESAMPLE clause can only be applied to tables and materialized views
LINE 2: SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEA...
^
SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
ERROR: syntax error at or near "TABLESAMPLE"
LINE 1: ...CT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPL...
^
-- catalog sanity
SELECT *
FROM pg_tablesample_method
WHERE tsminit IS NULL
OR tsmseqscan IS NULL
OR tsmpagemode IS NULL
OR tsmnextblock IS NULL
OR tsmnexttuple IS NULL
OR tsmend IS NULL
OR tsmreset IS NULL
OR tsmcost IS NULL;
tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost
---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
(0 rows)
-- done
DROP TABLE test_tablesample CASCADE;
NOTICE: drop cascades to 2 other objects
DETAIL: drop cascades to view test_tablesample_v1
drop cascades to view test_tablesample_v2

5
src/test/regress/output/misc.source
View File

@ -686,6 +686,9 @@ SELECT user_relns() AS user_relns
test_range_excl
test_range_gist
test_range_spgist
test_tablesample
test_tablesample_v1
test_tablesample_v2
test_tsvector
testjsonb
text_tbl
@ -705,7 +708,7 @@ SELECT user_relns() AS user_relns
tvvmv
varchar_tbl
xacttest
(127 rows)
(130 rows)
SELECT name(equipment(hobby_construct(text 'skywalking', text 'mer')));
name

2
src/test/regress/serial_schedule
View File

@ -110,6 +110,7 @@ test: lock
test: replica_identity
test: rowsecurity
test: object_address
test: tablesample
test: alter_generic
test: alter_operator
test: misc
@ -156,4 +157,3 @@ test: with
test: xml
test: event_trigger
test: stats
test: tablesample

8
src/test/regress/sql/rowsecurity.sql
View File

@ -94,14 +94,18 @@ SET row_security TO ON;
SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle) ORDER BY did;
SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
-- try a sampled version
SELECT * FROM document TABLESAMPLE BERNOULLI(50) REPEATABLE(0)
WHERE f_leak(dtitle) ORDER BY did;
-- viewpoint from rls_regress_user2
SET SESSION AUTHORIZATION rls_regress_user2;
SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle) ORDER BY did;
SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
-- try a sampled version
SELECT * FROM document TABLESAMPLE BERNOULLI(50) REPEATABLE(0)
WHERE f_leak(dtitle) ORDER BY did;
EXPLAIN (COSTS OFF) SELECT * FROM document WHERE f_leak(dtitle);
EXPLAIN (COSTS OFF) SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle);

90
src/test/regress/sql/tablesample.sql
View File

@ -1,26 +1,37 @@
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10);
-- use fillfactor so we don't have to load too much data to get multiple pages
INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
INSERT INTO test_tablesample
SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i);
SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (0);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (0);
-- 100% should give repeatable count results (ie, all rows) in any case
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (1+2);
SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (0.4);
CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
CREATE VIEW test_tablesample_v1 AS
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
CREATE VIEW test_tablesample_v2 AS
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
\d+ test_tablesample_v1
\d+ test_tablesample_v2
-- check a sampled query doesn't affect cursor in progress
BEGIN;
DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
DECLARE tablesample_cur CURSOR FOR
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
FETCH FIRST FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
FETCH NEXT FROM tablesample_cur;
FETCH NEXT FROM tablesample_cur;
@ -36,12 +47,45 @@ FETCH NEXT FROM tablesample_cur;
CLOSE tablesample_cur;
END;
EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
EXPLAIN SELECT * FROM test_tablesample_v1;
EXPLAIN (COSTS OFF)
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (2);
EXPLAIN (COSTS OFF)
SELECT * FROM test_tablesample_v1;
-- check inheritance behavior
explain (costs off)
select count(*) from person tablesample bernoulli (100);
select count(*) from person tablesample bernoulli (100);
select count(*) from person;
-- check that collations get assigned within the tablesample arguments
SELECT count(*) FROM test_tablesample TABLESAMPLE bernoulli (('1'::text < '0'::text)::int);
-- check behavior during rescans, as well as correct handling of min/max pct
select * from
(values (0),(100)) v(pct),
lateral (select count(*) from tenk1 tablesample bernoulli (pct)) ss;
select * from
(values (0),(100)) v(pct),
lateral (select count(*) from tenk1 tablesample system (pct)) ss;
explain (costs off)
select pct, count(unique1) from
(values (0),(100)) v(pct),
lateral (select * from tenk1 tablesample bernoulli (pct)) ss
group by pct;
select pct, count(unique1) from
(values (0),(100)) v(pct),
lateral (select * from tenk1 tablesample bernoulli (pct)) ss
group by pct;
select pct, count(unique1) from
(values (0),(100)) v(pct),
lateral (select * from tenk1 tablesample system (pct)) ss
group by pct;
-- errors
SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (NULL);
SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
@ -56,19 +100,3 @@ WITH query_select AS (SELECT * FROM test_tablesample)
SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
-- catalog sanity
SELECT *
FROM pg_tablesample_method
WHERE tsminit IS NULL
OR tsmseqscan IS NULL
OR tsmpagemode IS NULL
OR tsmnextblock IS NULL
OR tsmnexttuple IS NULL
OR tsmend IS NULL
OR tsmreset IS NULL
OR tsmcost IS NULL;
-- done
DROP TABLE test_tablesample CASCADE;