2015-05-15 20:37:10 +02:00
|
|
|
/*-------------------------------------------------------------------------
|
|
|
|
*
|
|
|
|
* nodeSamplescan.c
|
|
|
|
* Support routines for sample scans of relations (table sampling).
|
|
|
|
*
|
2019-01-02 18:44:25 +01:00
|
|
|
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
|
2015-05-15 20:37:10 +02:00
|
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
|
|
*
|
|
|
|
*
|
|
|
|
* IDENTIFICATION
|
|
|
|
* src/backend/executor/nodeSamplescan.c
|
|
|
|
*
|
|
|
|
*-------------------------------------------------------------------------
|
|
|
|
*/
|
|
|
|
#include "postgres.h"
|
|
|
|
|
Don't include heapam.h from others headers.
heapam.h previously was included in a number of widely used
headers (e.g. execnodes.h, indirectly in executor.h, ...). That's
problematic on its own, as heapam.h contains a lot of low-level
details that don't need to be exposed that widely, but becomes more
problematic with the upcoming introduction of pluggable table storage
- it seems inappropriate for heapam.h to be included that widely
afterwards.
heapam.h was largely only included in other headers to get the
HeapScanDesc typedef (which was defined in heapam.h, even though
HeapScanDescData is defined in relscan.h). The better solution here
seems to be to just use the underlying struct (forward declared where
necessary). Similar for BulkInsertState.
Another problem was that LockTupleMode was used in executor.h - parts
of the file tried to cope without heapam.h, but due to the fact that
it indirectly included it, several subsequent violations of that goal
were not not noticed. We could just reuse the approach of declaring
parameters as int, but it seems nicer to move LockTupleMode to
lockoptions.h - that's not a perfect location, but also doesn't seem
bad.
As a number of files relied on implicitly included heapam.h, a
significant number of files grew an explicit include. It's quite
probably that a few external projects will need to do the same.
Author: Andres Freund
Reviewed-By: Alvaro Herrera
Discussion: https://postgr.es/m/20190114000701.y4ttcb74jpskkcfb@alap3.anarazel.de
2019-01-15 00:54:18 +01:00
|
|
|
#include "access/heapam.h"
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
#include "access/relscan.h"
|
|
|
|
#include "access/tsmapi.h"
|
2015-05-15 20:37:10 +02:00
|
|
|
#include "executor/executor.h"
|
|
|
|
#include "executor/nodeSamplescan.h"
|
|
|
|
#include "miscadmin.h"
|
|
|
|
#include "pgstat.h"
|
2019-03-11 17:17:50 +01:00
|
|
|
#include "storage/bufmgr.h"
|
2015-05-15 20:37:10 +02:00
|
|
|
#include "storage/predicate.h"
|
2016-12-28 18:00:00 +01:00
|
|
|
#include "utils/builtins.h"
|
2015-05-15 20:37:10 +02:00
|
|
|
#include "utils/rel.h"
|
|
|
|
|
|
|
|
static TupleTableSlot *SampleNext(SampleScanState *node);
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
static void tablesample_init(SampleScanState *scanstate);
|
|
|
|
static HeapTuple tablesample_getnext(SampleScanState *scanstate);
|
|
|
|
static bool SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset,
|
|
|
|
HeapScanDesc scan);
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/* ----------------------------------------------------------------
|
|
|
|
* Scan Support
|
|
|
|
* ----------------------------------------------------------------
|
|
|
|
*/
|
|
|
|
|
|
|
|
/* ----------------------------------------------------------------
|
|
|
|
* SampleNext
|
|
|
|
*
|
|
|
|
* This is a workhorse for ExecSampleScan
|
|
|
|
* ----------------------------------------------------------------
|
|
|
|
*/
|
|
|
|
static TupleTableSlot *
|
|
|
|
SampleNext(SampleScanState *node)
|
|
|
|
{
|
2015-05-24 03:35:49 +02:00
|
|
|
HeapTuple tuple;
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
TupleTableSlot *slot;
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/*
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
* if this is first call within a scan, initialize
|
2015-05-15 20:37:10 +02:00
|
|
|
*/
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
if (!node->begun)
|
|
|
|
tablesample_init(node);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* get the next tuple, and store it in our result slot
|
|
|
|
*/
|
|
|
|
tuple = tablesample_getnext(node);
|
2015-05-15 20:37:10 +02:00
|
|
|
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
slot = node->ss.ss_ScanTupleSlot;
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
if (tuple)
|
2018-10-04 20:03:37 +02:00
|
|
|
ExecStoreBufferHeapTuple(tuple, /* tuple to store */
|
2018-09-26 01:27:48 +02:00
|
|
|
slot, /* slot to store in */
|
2018-10-04 20:03:37 +02:00
|
|
|
node->ss.ss_currentScanDesc->rs_cbuf); /* tuple's buffer */
|
2015-05-15 20:37:10 +02:00
|
|
|
else
|
|
|
|
ExecClearTuple(slot);
|
|
|
|
|
|
|
|
return slot;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
|
|
|
|
*/
|
|
|
|
static bool
|
|
|
|
SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
|
|
|
|
{
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
/*
|
|
|
|
* No need to recheck for SampleScan, since like SeqScan we don't pass any
|
|
|
|
* checkable keys to heap_beginscan.
|
|
|
|
*/
|
2015-05-15 20:37:10 +02:00
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* ----------------------------------------------------------------
|
|
|
|
* ExecSampleScan(node)
|
|
|
|
*
|
|
|
|
* Scans the relation using the sampling method and returns
|
|
|
|
* the next qualifying tuple.
|
|
|
|
* We call the ExecScan() routine and pass it the appropriate
|
|
|
|
* access method functions.
|
|
|
|
* ----------------------------------------------------------------
|
|
|
|
*/
|
2017-07-17 09:33:49 +02:00
|
|
|
static TupleTableSlot *
|
|
|
|
ExecSampleScan(PlanState *pstate)
|
2015-05-15 20:37:10 +02:00
|
|
|
{
|
2017-07-17 09:33:49 +02:00
|
|
|
SampleScanState *node = castNode(SampleScanState, pstate);
|
|
|
|
|
|
|
|
return ExecScan(&node->ss,
|
2015-05-15 20:37:10 +02:00
|
|
|
(ExecScanAccessMtd) SampleNext,
|
|
|
|
(ExecScanRecheckMtd) SampleRecheck);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* ----------------------------------------------------------------
|
|
|
|
* ExecInitSampleScan
|
|
|
|
* ----------------------------------------------------------------
|
|
|
|
*/
|
|
|
|
SampleScanState *
|
|
|
|
ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
|
|
|
|
{
|
|
|
|
SampleScanState *scanstate;
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
TableSampleClause *tsc = node->tablesample;
|
|
|
|
TsmRoutine *tsm;
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
Assert(outerPlan(node) == NULL);
|
|
|
|
Assert(innerPlan(node) == NULL);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* create state structure
|
|
|
|
*/
|
|
|
|
scanstate = makeNode(SampleScanState);
|
|
|
|
scanstate->ss.ps.plan = (Plan *) node;
|
|
|
|
scanstate->ss.ps.state = estate;
|
2017-07-17 09:33:49 +02:00
|
|
|
scanstate->ss.ps.ExecProcNode = ExecSampleScan;
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Miscellaneous initialization
|
|
|
|
*
|
|
|
|
* create expression context for node
|
|
|
|
*/
|
|
|
|
ExecAssignExprContext(estate, &scanstate->ss.ps);
|
|
|
|
|
|
|
|
/*
|
2018-10-06 21:49:37 +02:00
|
|
|
* open the scan relation
|
2015-05-15 20:37:10 +02:00
|
|
|
*/
|
2018-02-17 06:17:38 +01:00
|
|
|
scanstate->ss.ss_currentRelation =
|
|
|
|
ExecOpenScanRelation(estate,
|
|
|
|
node->scan.scanrelid,
|
|
|
|
eflags);
|
Faster expression evaluation and targetlist projection.
This replaces the old, recursive tree-walk based evaluation, with
non-recursive, opcode dispatch based, expression evaluation.
Projection is now implemented as part of expression evaluation.
This both leads to significant performance improvements, and makes
future just-in-time compilation of expressions easier.
The speed gains primarily come from:
- non-recursive implementation reduces stack usage / overhead
- simple sub-expressions are implemented with a single jump, without
function calls
- sharing some state between different sub-expressions
- reduced amount of indirect/hard to predict memory accesses by laying
out operation metadata sequentially; including the avoidance of
nearly all of the previously used linked lists
- more code has been moved to expression initialization, avoiding
constant re-checks at evaluation time
Future just-in-time compilation (JIT) has become easier, as
demonstrated by released patches intended to be merged in a later
release, for primarily two reasons: Firstly, due to a stricter split
between expression initialization and evaluation, less code has to be
handled by the JIT. Secondly, due to the non-recursive nature of the
generated "instructions", less performance-critical code-paths can
easily be shared between interpreted and compiled evaluation.
The new framework allows for significant future optimizations. E.g.:
- basic infrastructure for to later reduce the per executor-startup
overhead of expression evaluation, by caching state in prepared
statements. That'd be helpful in OLTPish scenarios where
initialization overhead is measurable.
- optimizing the generated "code". A number of proposals for potential
work has already been made.
- optimizing the interpreter. Similarly a number of proposals have
been made here too.
The move of logic into the expression initialization step leads to some
backward-incompatible changes:
- Function permission checks are now done during expression
initialization, whereas previously they were done during
execution. In edge cases this can lead to errors being raised that
previously wouldn't have been, e.g. a NULL array being coerced to a
different array type previously didn't perform checks.
- The set of domain constraints to be checked, is now evaluated once
during expression initialization, previously it was re-built
every time a domain check was evaluated. For normal queries this
doesn't change much, but e.g. for plpgsql functions, which caches
ExprStates, the old set could stick around longer. The behavior
around might still change.
Author: Andres Freund, with significant changes by Tom Lane,
changes by Heikki Linnakangas
Reviewed-By: Tom Lane, Heikki Linnakangas
Discussion: https://postgr.es/m/20161206034955.bh33paeralxbtluv@alap3.anarazel.de
2017-03-14 23:45:36 +01:00
|
|
|
|
2018-02-17 06:17:38 +01:00
|
|
|
/* we won't set up the HeapScanDesc till later */
|
|
|
|
scanstate->ss.ss_currentScanDesc = NULL;
|
2015-05-15 20:37:10 +02:00
|
|
|
|
2018-02-17 06:17:38 +01:00
|
|
|
/* and create slot with appropriate rowtype */
|
|
|
|
ExecInitScanTupleSlot(estate, &scanstate->ss,
|
Introduce notion of different types of slots (without implementing them).
Upcoming work intends to allow pluggable ways to introduce new ways of
storing table data. Accessing those table access methods from the
executor requires TupleTableSlots to be carry tuples in the native
format of such storage methods; otherwise there'll be a significant
conversion overhead.
Different access methods will require different data to store tuples
efficiently (just like virtual, minimal, heap already require fields
in TupleTableSlot). To allow that without requiring additional pointer
indirections, we want to have different structs (embedding
TupleTableSlot) for different types of slots. Thus different types of
slots are needed, which requires adapting creators of slots.
The slot that most efficiently can represent a type of tuple in an
executor node will often depend on the type of slot a child node
uses. Therefore we need to track the type of slot is returned by
nodes, so parent slots can create slots based on that.
Relatedly, JIT compilation of tuple deforming needs to know which type
of slot a certain expression refers to, so it can create an
appropriate deforming function for the type of tuple in the slot.
But not all nodes will only return one type of slot, e.g. an append
node will potentially return different types of slots for each of its
subplans.
Therefore add function that allows to query the type of a node's
result slot, and whether it'll always be the same type (whether it's
fixed). This can be queried using ExecGetResultSlotOps().
The scan, result, inner, outer type of slots are automatically
inferred from ExecInitScanTupleSlot(), ExecInitResultSlot(),
left/right subtrees respectively. If that's not correct for a node,
that can be overwritten using new fields in PlanState.
This commit does not introduce the actually abstracted implementation
of different kind of TupleTableSlots, that will be left for a followup
commit. The different types of slots introduced will, for now, still
use the same backing implementation.
While this already partially invalidates the big comment in
tuptable.h, it seems to make more sense to update it later, when the
different TupleTableSlot implementations actually exist.
Author: Ashutosh Bapat and Andres Freund, with changes by Amit Khandekar
Discussion: https://postgr.es/m/20181105210039.hh4vvi4vwoq5ba2q@alap3.anarazel.de
2018-11-16 07:00:30 +01:00
|
|
|
RelationGetDescr(scanstate->ss.ss_currentRelation),
|
Make TupleTableSlots extensible, finish split of existing slot type.
This commit completes the work prepared in 1a0586de36, splitting the
old TupleTableSlot implementation (which could store buffer, heap,
minimal and virtual slots) into four different slot types. As
described in the aforementioned commit, this is done with the goal of
making tuple table slots extensible, to allow for pluggable table
access methods.
To achieve runtime extensibility for TupleTableSlots, operations on
slots that can differ between types of slots are performed using the
TupleTableSlotOps struct provided at slot creation time. That
includes information from the size of TupleTableSlot struct to be
allocated, initialization, deforming etc. See the struct's definition
for more detailed information about callbacks TupleTableSlotOps.
I decided to rename TTSOpsBufferTuple to TTSOpsBufferHeapTuple and
ExecCopySlotTuple to ExecCopySlotHeapTuple, as that seems more
consistent with other naming introduced in recent patches.
There's plenty optimization potential in the slot implementation, but
according to benchmarking the state after this commit has similar
performance characteristics to before this set of changes, which seems
sufficient.
There's a few changes in execReplication.c that currently need to poke
through the slot abstraction, that'll be repaired once the pluggable
storage patchset provides the necessary infrastructure.
Author: Andres Freund and Ashutosh Bapat, with changes by Amit Khandekar
Discussion: https://postgr.es/m/20181105210039.hh4vvi4vwoq5ba2q@alap3.anarazel.de
2018-11-17 01:35:11 +01:00
|
|
|
&TTSOpsBufferHeapTuple);
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/*
|
Don't require return slots for nodes without projection.
In a lot of nodes the return slot is not required. That can either be
because the node doesn't do any projection (say an Append node), or
because the node does perform projections but the projection is
optimized away because the projection would yield an identical row.
Slots aren't that small, especially for wide rows, so it's worthwhile
to avoid creating them. It's not possible to just skip creating the
slot - it's currently used to determine the tuple descriptor returned
by ExecGetResultType(). So separate the determination of the result
type from the slot creation. The work previously done internally
ExecInitResultTupleSlotTL() can now also be done separately with
ExecInitResultTypeTL() and ExecInitResultSlot(). That way nodes that
aren't guaranteed to need a result slot, can use
ExecInitResultTypeTL() to determine the result type of the node, and
ExecAssignScanProjectionInfo() (via
ExecConditionalAssignProjectionInfo()) determines that a result slot
is needed, it is created with ExecInitResultSlot().
Besides the advantage of avoiding to create slots that then are
unused, this is necessary preparation for later patches around tuple
table slot abstraction. In particular separating the return descriptor
and slot is a prerequisite to allow JITing of tuple deforming with
knowledge of the underlying tuple format, and to avoid unnecessarily
creating JITed tuple deforming for virtual slots.
This commit removes a redundant argument from
ExecInitResultTupleSlotTL(). While this commit touches a lot of the
relevant lines anyway, it'd normally still not worthwhile to cause
breakage, except that aforementioned later commits will touch *all*
ExecInitResultTupleSlotTL() callers anyway (but fits worse
thematically).
Author: Andres Freund
Discussion: https://postgr.es/m/20181105210039.hh4vvi4vwoq5ba2q@alap3.anarazel.de
2018-11-10 02:19:39 +01:00
|
|
|
* Initialize result type and projection.
|
2015-05-15 20:37:10 +02:00
|
|
|
*/
|
Don't require return slots for nodes without projection.
In a lot of nodes the return slot is not required. That can either be
because the node doesn't do any projection (say an Append node), or
because the node does perform projections but the projection is
optimized away because the projection would yield an identical row.
Slots aren't that small, especially for wide rows, so it's worthwhile
to avoid creating them. It's not possible to just skip creating the
slot - it's currently used to determine the tuple descriptor returned
by ExecGetResultType(). So separate the determination of the result
type from the slot creation. The work previously done internally
ExecInitResultTupleSlotTL() can now also be done separately with
ExecInitResultTypeTL() and ExecInitResultSlot(). That way nodes that
aren't guaranteed to need a result slot, can use
ExecInitResultTypeTL() to determine the result type of the node, and
ExecAssignScanProjectionInfo() (via
ExecConditionalAssignProjectionInfo()) determines that a result slot
is needed, it is created with ExecInitResultSlot().
Besides the advantage of avoiding to create slots that then are
unused, this is necessary preparation for later patches around tuple
table slot abstraction. In particular separating the return descriptor
and slot is a prerequisite to allow JITing of tuple deforming with
knowledge of the underlying tuple format, and to avoid unnecessarily
creating JITed tuple deforming for virtual slots.
This commit removes a redundant argument from
ExecInitResultTupleSlotTL(). While this commit touches a lot of the
relevant lines anyway, it'd normally still not worthwhile to cause
breakage, except that aforementioned later commits will touch *all*
ExecInitResultTupleSlotTL() callers anyway (but fits worse
thematically).
Author: Andres Freund
Discussion: https://postgr.es/m/20181105210039.hh4vvi4vwoq5ba2q@alap3.anarazel.de
2018-11-10 02:19:39 +01:00
|
|
|
ExecInitResultTypeTL(&scanstate->ss.ps);
|
2018-02-17 06:17:38 +01:00
|
|
|
ExecAssignScanProjectionInfo(&scanstate->ss);
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/*
|
2018-02-17 06:17:38 +01:00
|
|
|
* initialize child expressions
|
2015-05-15 20:37:10 +02:00
|
|
|
*/
|
2018-02-17 06:17:38 +01:00
|
|
|
scanstate->ss.ps.qual =
|
|
|
|
ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
|
|
|
|
|
|
|
|
scanstate->args = ExecInitExprList(tsc->args, (PlanState *) scanstate);
|
|
|
|
scanstate->repeatable =
|
|
|
|
ExecInitExpr(tsc->repeatable, (PlanState *) scanstate);
|
2015-05-15 20:37:10 +02:00
|
|
|
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
/*
|
|
|
|
* 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;
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
return scanstate;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* ----------------------------------------------------------------
|
|
|
|
* ExecEndSampleScan
|
|
|
|
*
|
|
|
|
* frees any storage allocated through C routines.
|
|
|
|
* ----------------------------------------------------------------
|
|
|
|
*/
|
|
|
|
void
|
|
|
|
ExecEndSampleScan(SampleScanState *node)
|
|
|
|
{
|
|
|
|
/*
|
|
|
|
* Tell sampling function that we finished the scan.
|
|
|
|
*/
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
if (node->tsmroutine->EndSampleScan)
|
|
|
|
node->tsmroutine->EndSampleScan(node);
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Free the exprcontext
|
|
|
|
*/
|
|
|
|
ExecFreeExprContext(&node->ss.ps);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* clean out the tuple table
|
|
|
|
*/
|
Don't require return slots for nodes without projection.
In a lot of nodes the return slot is not required. That can either be
because the node doesn't do any projection (say an Append node), or
because the node does perform projections but the projection is
optimized away because the projection would yield an identical row.
Slots aren't that small, especially for wide rows, so it's worthwhile
to avoid creating them. It's not possible to just skip creating the
slot - it's currently used to determine the tuple descriptor returned
by ExecGetResultType(). So separate the determination of the result
type from the slot creation. The work previously done internally
ExecInitResultTupleSlotTL() can now also be done separately with
ExecInitResultTypeTL() and ExecInitResultSlot(). That way nodes that
aren't guaranteed to need a result slot, can use
ExecInitResultTypeTL() to determine the result type of the node, and
ExecAssignScanProjectionInfo() (via
ExecConditionalAssignProjectionInfo()) determines that a result slot
is needed, it is created with ExecInitResultSlot().
Besides the advantage of avoiding to create slots that then are
unused, this is necessary preparation for later patches around tuple
table slot abstraction. In particular separating the return descriptor
and slot is a prerequisite to allow JITing of tuple deforming with
knowledge of the underlying tuple format, and to avoid unnecessarily
creating JITed tuple deforming for virtual slots.
This commit removes a redundant argument from
ExecInitResultTupleSlotTL(). While this commit touches a lot of the
relevant lines anyway, it'd normally still not worthwhile to cause
breakage, except that aforementioned later commits will touch *all*
ExecInitResultTupleSlotTL() callers anyway (but fits worse
thematically).
Author: Andres Freund
Discussion: https://postgr.es/m/20181105210039.hh4vvi4vwoq5ba2q@alap3.anarazel.de
2018-11-10 02:19:39 +01:00
|
|
|
if (node->ss.ps.ps_ResultTupleSlot)
|
|
|
|
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
|
2015-05-15 20:37:10 +02:00
|
|
|
ExecClearTuple(node->ss.ss_ScanTupleSlot);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* close heap scan
|
|
|
|
*/
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
if (node->ss.ss_currentScanDesc)
|
|
|
|
heap_endscan(node->ss.ss_currentScanDesc);
|
2015-05-15 20:37:10 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
/* ----------------------------------------------------------------
|
|
|
|
* ExecReScanSampleScan
|
|
|
|
*
|
|
|
|
* Rescans the relation.
|
|
|
|
*
|
|
|
|
* ----------------------------------------------------------------
|
|
|
|
*/
|
|
|
|
void
|
|
|
|
ExecReScanSampleScan(SampleScanState *node)
|
|
|
|
{
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
/* 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,
|
2017-01-19 23:12:38 +01:00
|
|
|
&isnull);
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
if (isnull)
|
|
|
|
ereport(ERROR,
|
|
|
|
(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
|
|
|
|
errmsg("TABLESAMPLE parameter cannot be null")));
|
|
|
|
i++;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (scanstate->repeatable)
|
|
|
|
{
|
|
|
|
datum = ExecEvalExprSwitchContext(scanstate->repeatable,
|
|
|
|
econtext,
|
2017-01-19 23:12:38 +01:00
|
|
|
&isnull);
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
if (isnull)
|
|
|
|
ereport(ERROR,
|
|
|
|
(errcode(ERRCODE_INVALID_TABLESAMPLE_REPEAT),
|
Phase 3 of pgindent updates.
Don't move parenthesized lines to the left, even if that means they
flow past the right margin.
By default, BSD indent lines up statement continuation lines that are
within parentheses so that they start just to the right of the preceding
left parenthesis. However, traditionally, if that resulted in the
continuation line extending to the right of the desired right margin,
then indent would push it left just far enough to not overrun the margin,
if it could do so without making the continuation line start to the left of
the current statement indent. That makes for a weird mix of indentations
unless one has been completely rigid about never violating the 80-column
limit.
This behavior has been pretty universally panned by Postgres developers.
Hence, disable it with indent's new -lpl switch, so that parenthesized
lines are always lined up with the preceding left paren.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 21:35:54 +02:00
|
|
|
errmsg("TABLESAMPLE REPEATABLE parameter cannot be null")));
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
|
|
|
|
/*
|
|
|
|
* 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 */
|
Phase 2 of pgindent updates.
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
2017-06-21 21:18:54 +02:00
|
|
|
blockno = scan->rs_cblock; /* current page */
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
}
|
2015-05-15 20:37:10 +02:00
|
|
|
|
|
|
|
/*
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
* When not using pagemode, we must lock the buffer during tuple
|
|
|
|
* visibility checks.
|
2015-05-15 20:37:10 +02:00
|
|
|
*/
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
if (!pagemode)
|
|
|
|
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
|
|
|
|
|
2016-04-20 15:31:19 +02:00
|
|
|
page = (Page) BufferGetPage(scan->rs_cbuf);
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
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);
|
|
|
|
|
2016-04-20 15:31:19 +02:00
|
|
|
page = (Page) BufferGetPage(scan->rs_cbuf);
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
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);
|
|
|
|
}
|
2015-05-15 20:37:10 +02:00
|
|
|
|
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.
2015-07-25 20:39:00 +02:00
|
|
|
/*
|
|
|
|
* 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);
|
|
|
|
}
|
2015-05-15 20:37:10 +02:00
|
|
|
}
|