postgresql/contrib/postgres_fdw/postgres_fdw.c
Tom Lane 21734d2fb8 Support writable foreign tables.
This patch adds the core-system infrastructure needed to support updates
on foreign tables, and extends contrib/postgres_fdw to allow updates
against remote Postgres servers.  There's still a great deal of room for
improvement in optimization of remote updates, but at least there's basic
functionality there now.

KaiGai Kohei, reviewed by Alexander Korotkov and Laurenz Albe, and rather
heavily revised by Tom Lane.
2013-03-10 14:16:02 -04:00

2283 lines
65 KiB
C

/*-------------------------------------------------------------------------
*
* postgres_fdw.c
* Foreign-data wrapper for remote PostgreSQL servers
*
* Portions Copyright (c) 2012-2013, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/postgres_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
PG_MODULE_MAGIC;
/* Default CPU cost to start up a foreign query. */
#define DEFAULT_FDW_STARTUP_COST 100.0
/* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */
#define DEFAULT_FDW_TUPLE_COST 0.01
/*
* FDW-specific planner information kept in RelOptInfo.fdw_private for a
* foreign table. This information is collected by postgresGetForeignRelSize.
*/
typedef struct PgFdwRelationInfo
{
/* XXX underdocumented, but a lot of this shouldn't be here anyway */
StringInfoData sql;
Cost startup_cost;
Cost total_cost;
List *remote_conds;
List *param_conds;
List *local_conds;
List *param_numbers;
/* Cached catalog information. */
ForeignTable *table;
ForeignServer *server;
} PgFdwRelationInfo;
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
* We store various information in ForeignScan.fdw_private to pass it from
* planner to executor. Specifically there is:
*
* 1) SELECT statement text to be sent to the remote server
* 2) IDs of PARAM_EXEC Params used in the SELECT statement
*
* These items are indexed with the enum FdwScanPrivateIndex, so an item
* can be fetched with list_nth(). For example, to get the SELECT statement:
* sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
*/
enum FdwScanPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwScanPrivateSelectSql,
/* Integer list of param IDs of PARAM_EXEC Params used in SQL stmt */
FdwScanPrivateExternParamIds
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ModifyTable node referencing a postgres_fdw foreign table. We store:
*
* 1) INSERT/UPDATE/DELETE statement text to be sent to the remote server
* 2) Integer list of target attribute numbers for INSERT/UPDATE
* (NIL for a DELETE)
* 3) Boolean flag showing if there's a RETURNING clause
*/
enum FdwModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwModifyPrivateUpdateSql,
/* Integer list of target attribute numbers for INSERT/UPDATE */
FdwModifyPrivateTargetAttnums,
/* has-returning flag (as an integer Value node) */
FdwModifyPrivateHasReturning
};
/*
* Execution state of a foreign scan using postgres_fdw.
*/
typedef struct PgFdwScanState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
List *fdw_private; /* FDW-private information from planner */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
unsigned int cursor_number; /* quasi-unique ID for my cursor */
bool cursor_exists; /* have we created the cursor? */
bool extparams_done; /* have we converted PARAM_EXTERN params? */
int numParams; /* number of parameters passed to query */
Oid *param_types; /* array of types of query parameters */
const char **param_values; /* array of values of query parameters */
/* for storing result tuples */
HeapTuple *tuples; /* array of currently-retrieved tuples */
int num_tuples; /* # of tuples in array */
int next_tuple; /* index of next one to return */
/* batch-level state, for optimizing rewinds and avoiding useless fetch */
int fetch_ct_2; /* Min(# of fetches done, 2) */
bool eof_reached; /* true if last fetch reached EOF */
/* working memory contexts */
MemoryContext batch_cxt; /* context holding current batch of tuples */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwScanState;
/*
* Execution state of a foreign insert/update/delete operation.
*/
typedef struct PgFdwModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
char *p_name; /* name of prepared statement, if created */
/* extracted fdw_private data */
char *query; /* text of INSERT/UPDATE/DELETE command */
List *target_attrs; /* list of target attribute numbers */
bool has_returning; /* is there a RETURNING clause? */
/* info about parameters for prepared statement */
AttrNumber ctidAttno; /* attnum of input resjunk ctid column */
int p_nums; /* number of parameters to transmit */
FmgrInfo *p_flinfo; /* output conversion functions for them */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwModifyState;
/*
* Workspace for analyzing a foreign table.
*/
typedef struct PgFdwAnalyzeState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* collected sample rows */
HeapTuple *rows; /* array of size targrows */
int targrows; /* target # of sample rows */
int numrows; /* # of sample rows collected */
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
double rstate; /* random state */
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwAnalyzeState;
/*
* Identify the attribute where data conversion fails.
*/
typedef struct ConversionLocation
{
Relation rel; /* foreign table's relcache entry */
AttrNumber cur_attno; /* attribute number being processed, or 0 */
} ConversionLocation;
/*
* SQL functions
*/
extern Datum postgres_fdw_handler(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(postgres_fdw_handler);
/*
* FDW callback routines
*/
static void postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static void postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static ForeignScan *postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses);
static void postgresBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node);
static void postgresReScanForeignScan(ForeignScanState *node);
static void postgresEndForeignScan(ForeignScanState *node);
static void postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation);
static List *postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags);
static TupleTableSlot *postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo);
static void postgresExplainForeignScan(ForeignScanState *node,
ExplainState *es);
static void postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es);
static bool postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages);
/*
* Helper functions
*/
static void get_remote_estimate(const char *sql,
PGconn *conn,
double *rows,
int *width,
Cost *startup_cost,
Cost *total_cost);
static void create_cursor(ForeignScanState *node);
static void fetch_more_data(ForeignScanState *node);
static void close_cursor(PGconn *conn, unsigned int cursor_number);
static void prepare_foreign_modify(PgFdwModifyState *fmstate);
static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot);
static void store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res);
static int postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows);
static void analyze_row_processor(PGresult *res, int row,
PgFdwAnalyzeState *astate);
static HeapTuple make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
MemoryContext temp_context);
static void conversion_error_callback(void *arg);
/*
* Foreign-data wrapper handler function: return a struct with pointers
* to my callback routines.
*/
Datum
postgres_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *routine = makeNode(FdwRoutine);
/* Functions for scanning foreign tables */
routine->GetForeignRelSize = postgresGetForeignRelSize;
routine->GetForeignPaths = postgresGetForeignPaths;
routine->GetForeignPlan = postgresGetForeignPlan;
routine->BeginForeignScan = postgresBeginForeignScan;
routine->IterateForeignScan = postgresIterateForeignScan;
routine->ReScanForeignScan = postgresReScanForeignScan;
routine->EndForeignScan = postgresEndForeignScan;
/* Functions for updating foreign tables */
routine->AddForeignUpdateTargets = postgresAddForeignUpdateTargets;
routine->PlanForeignModify = postgresPlanForeignModify;
routine->BeginForeignModify = postgresBeginForeignModify;
routine->ExecForeignInsert = postgresExecForeignInsert;
routine->ExecForeignUpdate = postgresExecForeignUpdate;
routine->ExecForeignDelete = postgresExecForeignDelete;
routine->EndForeignModify = postgresEndForeignModify;
/* Support functions for EXPLAIN */
routine->ExplainForeignScan = postgresExplainForeignScan;
routine->ExplainForeignModify = postgresExplainForeignModify;
/* Support functions for ANALYZE */
routine->AnalyzeForeignTable = postgresAnalyzeForeignTable;
PG_RETURN_POINTER(routine);
}
/*
* postgresGetForeignRelSize
* Estimate # of rows and width of the result of the scan
*
* Here we estimate number of rows returned by the scan in two steps. In the
* first step, we execute remote EXPLAIN command to obtain the number of rows
* returned from remote side. In the second step, we calculate the selectivity
* of the filtering done on local side, and modify first estimate.
*
* We have to get some catalog objects and generate remote query string here,
* so we store such expensive information in FDW private area of RelOptInfo and
* pass them to subsequent functions for reuse.
*/
static void
postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
bool use_remote_estimate = false;
PgFdwRelationInfo *fpinfo;
StringInfo sql;
ForeignTable *table;
ForeignServer *server;
Selectivity sel;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
Cost run_cost;
QualCost qpqual_cost;
Cost cpu_per_tuple;
List *remote_conds;
List *param_conds;
List *local_conds;
List *param_numbers;
Bitmapset *attrs_used;
ListCell *lc;
/*
* We use PgFdwRelationInfo to pass various information to subsequent
* functions.
*/
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
initStringInfo(&fpinfo->sql);
sql = &fpinfo->sql;
/*
* Determine whether we use remote estimate or not. Note that per-table
* setting overrides per-server setting.
*/
table = GetForeignTable(foreigntableid);
server = GetForeignServer(table->serverid);
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
{
use_remote_estimate = defGetBoolean(def);
break;
}
}
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
{
use_remote_estimate = defGetBoolean(def);
break;
}
}
/*
* Identify which restriction clauses can be sent to the remote server and
* which can't. Conditions that are remotely executable but contain
* PARAM_EXTERN Params have to be treated separately because we can't use
* placeholders in remote EXPLAIN.
*/
classifyConditions(root, baserel, &remote_conds, &param_conds,
&local_conds, &param_numbers);
/*
* Identify which attributes will need to be retrieved from the remote
* server. These include all attrs needed for joins or final output, plus
* all attrs used in the local_conds.
*/
attrs_used = NULL;
pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
&attrs_used);
foreach(lc, local_conds)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&attrs_used);
}
/*
* Construct remote query which consists of SELECT, FROM, and WHERE
* clauses. For now, leave out the param_conds.
*/
deparseSelectSql(sql, root, baserel, attrs_used);
if (remote_conds)
appendWhereClause(sql, root, remote_conds, true);
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN with the quals that
* don't contain any Param nodes. Otherwise, estimate rows using whatever
* statistics we have locally, in a way similar to ordinary tables.
*/
if (use_remote_estimate)
{
RangeTblEntry *rte;
Oid userid;
UserMapping *user;
PGconn *conn;
/*
* Identify which user to do the remote access as. This should match
* what ExecCheckRTEPerms() does. If we fail due to lack of
* permissions, the query would have failed at runtime anyway.
*/
rte = planner_rt_fetch(baserel->relid, root);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
user = GetUserMapping(userid, server->serverid);
conn = GetConnection(server, user, false);
get_remote_estimate(sql->data, conn, &rows, &width,
&startup_cost, &total_cost);
ReleaseConnection(conn);
/*
* Estimate selectivity of conditions which were not used in remote
* EXPLAIN by calling clauselist_selectivity(). The best we can do
* for these conditions is to estimate selectivity on the basis of
* local statistics.
*/
sel = clauselist_selectivity(root, param_conds,
baserel->relid, JOIN_INNER, NULL);
sel *= clauselist_selectivity(root, local_conds,
baserel->relid, JOIN_INNER, NULL);
/*
* Add in the eval cost of those conditions, too.
*/
cost_qual_eval(&qpqual_cost, param_conds, root);
startup_cost += qpqual_cost.startup;
total_cost += qpqual_cost.per_tuple * rows;
cost_qual_eval(&qpqual_cost, local_conds, root);
startup_cost += qpqual_cost.startup;
total_cost += qpqual_cost.per_tuple * rows;
/* Report estimated numbers to planner. */
baserel->rows = clamp_row_est(rows * sel);
baserel->width = width;
}
else
{
/*
* Estimate rows from the result of the last ANALYZE, using all
* conditions specified in original query.
*
* If the foreign table has never been ANALYZEd, it will have relpages
* and reltuples equal to zero, which most likely has nothing to do
* with reality. We can't do a whole lot about that if we're not
* allowed to consult the remote server, but we can use a hack similar
* to plancat.c's treatment of empty relations: use a minimum size
* estimate of 10 pages, and divide by the column-datatype-based width
* estimate to get the corresponding number of tuples.
*/
if (baserel->pages == 0 && baserel->tuples == 0)
{
baserel->pages = 10;
baserel->tuples =
(10 * BLCKSZ) / (baserel->width + sizeof(HeapTupleHeaderData));
}
set_baserel_size_estimates(root, baserel);
/* Cost as though this were a seqscan, which is pessimistic. */
startup_cost = 0;
run_cost = 0;
run_cost += seq_page_cost * baserel->pages;
startup_cost += baserel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost.per_tuple;
run_cost += cpu_per_tuple * baserel->tuples;
total_cost = startup_cost + run_cost;
}
/*
* Finish deparsing remote query by adding conditions which were unusable
* in remote EXPLAIN because they contain Param nodes.
*/
if (param_conds)
appendWhereClause(sql, root, param_conds, (remote_conds == NIL));
/*
* Add FOR UPDATE/SHARE if appropriate. We apply locking during the
* initial row fetch, rather than later on as is done for local tables.
* The extra roundtrips involved in trying to duplicate the local
* semantics exactly don't seem worthwhile (see also comments for
* RowMarkType).
*/
if (baserel->relid == root->parse->resultRelation &&
(root->parse->commandType == CMD_UPDATE ||
root->parse->commandType == CMD_DELETE))
{
/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
appendStringInfo(sql, " FOR UPDATE");
}
else
{
RowMarkClause *rc = get_parse_rowmark(root->parse, baserel->relid);
if (rc)
{
/*
* Relation is specified as a FOR UPDATE/SHARE target, so handle
* that.
*
* For now, just ignore any [NO] KEY specification, since (a) it's
* not clear what that means for a remote table that we don't have
* complete information about, and (b) it wouldn't work anyway on
* older remote servers. Likewise, we don't worry about NOWAIT.
*/
switch (rc->strength)
{
case LCS_FORKEYSHARE:
case LCS_FORSHARE:
appendStringInfo(sql, " FOR SHARE");
break;
case LCS_FORNOKEYUPDATE:
case LCS_FORUPDATE:
appendStringInfo(sql, " FOR UPDATE");
break;
}
}
}
/*
* Store obtained information into FDW-private area of RelOptInfo so it's
* available to subsequent functions.
*/
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
fpinfo->remote_conds = remote_conds;
fpinfo->param_conds = param_conds;
fpinfo->local_conds = local_conds;
fpinfo->param_numbers = param_numbers;
fpinfo->table = table;
fpinfo->server = server;
baserel->fdw_private = (void *) fpinfo;
}
/*
* postgresGetForeignPaths
* Create possible scan paths for a scan on the foreign table
*/
static void
postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
ForeignPath *path;
ListCell *lc;
double fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
double fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
Cost startup_cost;
Cost total_cost;
List *fdw_private;
/*
* Check for user override of fdw_startup_cost, fdw_tuple_cost values
*/
foreach(lc, fpinfo->server->options)
{
DefElem *d = (DefElem *) lfirst(lc);
if (strcmp(d->defname, "fdw_startup_cost") == 0)
fdw_startup_cost = strtod(defGetString(d), NULL);
else if (strcmp(d->defname, "fdw_tuple_cost") == 0)
fdw_tuple_cost = strtod(defGetString(d), NULL);
}
/*
* We have cost values which are estimated on remote side, so adjust them
* for better estimate which respect various stuffs to complete the scan,
* such as sending query, transferring result, and local filtering.
*/
startup_cost = fpinfo->startup_cost;
total_cost = fpinfo->total_cost;
/*----------
* Adjust costs with factors of the corresponding foreign server:
* - add cost to establish connection to both startup and total
* - add cost to manipulate on remote, and transfer result to total
* - add cost to manipulate tuples on local side to total
*----------
*/
startup_cost += fdw_startup_cost;
total_cost += fdw_startup_cost;
total_cost += fdw_tuple_cost * baserel->rows;
total_cost += cpu_tuple_cost * baserel->rows;
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwScanPrivateIndex, above.
*/
fdw_private = list_make2(makeString(fpinfo->sql.data),
fpinfo->param_numbers);
/*
* Create simplest ForeignScan path node and add it to baserel. This path
* corresponds to SeqScan path of regular tables (though depending on what
* baserestrict conditions we were able to send to remote, there might
* actually be an indexscan happening there).
*/
path = create_foreignscan_path(root, baserel,
baserel->rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
NULL, /* no outer rel either */
fdw_private);
add_path(baserel, (Path *) path);
/*
* XXX We can consider sorted path or parameterized path here if we know
* that foreign table is indexed on remote end. For this purpose, we
* might have to support FOREIGN INDEX to represent possible sets of sort
* keys and/or filtering. Or we could just try some join conditions and
* see if remote side estimates using them as markedly cheaper. Note that
* executor functions need work to support internal Params before we can
* try generating any parameterized paths, though.
*/
}
/*
* postgresGetForeignPlan
* Create ForeignScan plan node which implements selected best path
*/
static ForeignScan *
postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
Index scan_relid = baserel->relid;
List *fdw_private = best_path->fdw_private;
List *remote_exprs = NIL;
List *local_exprs = NIL;
ListCell *lc;
/*
* Separate the scan_clauses into those that can be executed remotely and
* those that can't. For now, we accept only remote clauses that were
* previously determined to be safe by classifyClauses (so, only
* baserestrictinfo clauses can be used that way).
*
* This code must match "extract_actual_clauses(scan_clauses, false)"
* except for the additional decision about remote versus local execution.
*/
foreach(lc, scan_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
/* Ignore any pseudoconstants, they're dealt with elsewhere */
if (rinfo->pseudoconstant)
continue;
/* Either simple or parameterized remote clauses are OK now */
if (list_member_ptr(fpinfo->remote_conds, rinfo) ||
list_member_ptr(fpinfo->param_conds, rinfo))
remote_exprs = lappend(remote_exprs, rinfo->clause);
else
local_exprs = lappend(local_exprs, rinfo->clause);
}
/*
* Create the ForeignScan node from target list, local filtering
* expressions, remote filtering expressions, and FDW private information.
*
* Note that the remote_exprs are stored in the fdw_exprs field of the
* finished plan node; we can't keep them in private state because then
* they wouldn't be subject to later planner processing.
*
* XXX Currently, the remote_exprs aren't actually used at runtime, so we
* don't need to store them at all. But we'll keep this behavior for a
* little while for debugging reasons.
*/
return make_foreignscan(tlist,
local_exprs,
scan_relid,
remote_exprs,
fdw_private);
}
/*
* postgresBeginForeignScan
* Initiate an executor scan of a foreign PostgreSQL table.
*/
static void
postgresBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwScanState *fsstate;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
List *param_numbers;
int numParams;
int i;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
fsstate = (PgFdwScanState *) palloc0(sizeof(PgFdwScanState));
node->fdw_state = (void *) fsstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
rte = rt_fetch(fsplan->scan.scanrelid, estate->es_range_table);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
fsstate->rel = node->ss.ss_currentRelation;
table = GetForeignTable(RelationGetRelid(fsstate->rel));
server = GetForeignServer(table->serverid);
user = GetUserMapping(userid, server->serverid);
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
fsstate->conn = GetConnection(server, user, false);
/* Assign a unique ID for my cursor */
fsstate->cursor_number = GetCursorNumber(fsstate->conn);
fsstate->cursor_exists = false;
/* Get private info created by planner functions. */
fsstate->fdw_private = fsplan->fdw_private;
/* Create contexts for batches of tuples and per-tuple temp workspace. */
fsstate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw tuple data",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
fsstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/* Get info we'll need for data conversion. */
fsstate->attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(fsstate->rel));
/*
* Allocate buffer for query parameters, if the remote conditions use any.
*
* We use a parameter slot for each PARAM_EXTERN parameter, even though
* not all of them may get sent to the remote server. This allows us to
* refer to Params by their original number rather than remapping, and it
* doesn't cost much. Slots that are not actually used get filled with
* null values that are arbitrarily marked as being of type int4.
*/
param_numbers = (List *)
list_nth(fsstate->fdw_private, FdwScanPrivateExternParamIds);
if (param_numbers != NIL)
{
ParamListInfo params = estate->es_param_list_info;
numParams = params ? params->numParams : 0;
}
else
numParams = 0;
fsstate->numParams = numParams;
if (numParams > 0)
{
/* we initially fill all slots with value = NULL, type = int4 */
fsstate->param_types = (Oid *) palloc(numParams * sizeof(Oid));
fsstate->param_values = (const char **) palloc0(numParams * sizeof(char *));
for (i = 0; i < numParams; i++)
fsstate->param_types[i] = INT4OID;
}
else
{
fsstate->param_types = NULL;
fsstate->param_values = NULL;
}
fsstate->extparams_done = false;
}
/*
* postgresIterateForeignScan
* Retrieve next row from the result set, or clear tuple slot to indicate
* EOF.
*/
static TupleTableSlot *
postgresIterateForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
/*
* If this is the first call after Begin or ReScan, we need to create the
* cursor on the remote side.
*/
if (!fsstate->cursor_exists)
create_cursor(node);
/*
* Get some more tuples, if we've run out.
*/
if (fsstate->next_tuple >= fsstate->num_tuples)
{
/* No point in another fetch if we already detected EOF, though. */
if (!fsstate->eof_reached)
fetch_more_data(node);
/* If we didn't get any tuples, must be end of data. */
if (fsstate->next_tuple >= fsstate->num_tuples)
return ExecClearTuple(slot);
}
/*
* Return the next tuple.
*/
ExecStoreTuple(fsstate->tuples[fsstate->next_tuple++],
slot,
InvalidBuffer,
false);
return slot;
}
/*
* postgresReScanForeignScan
* Restart the scan.
*/
static void
postgresReScanForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
char sql[64];
PGresult *res;
/*
* Note: we assume that PARAM_EXTERN params don't change over the life of
* the query, so no need to reset extparams_done.
*/
/* If we haven't created the cursor yet, nothing to do. */
if (!fsstate->cursor_exists)
return;
/*
* If any internal parameters affecting this node have changed, we'd
* better destroy and recreate the cursor. Otherwise, rewinding it should
* be good enough. If we've only fetched zero or one batch, we needn't
* even rewind the cursor, just rescan what we have.
*/
if (node->ss.ps.chgParam != NULL)
{
fsstate->cursor_exists = false;
snprintf(sql, sizeof(sql), "CLOSE c%u",
fsstate->cursor_number);
}
else if (fsstate->fetch_ct_2 > 1)
{
snprintf(sql, sizeof(sql), "MOVE BACKWARD ALL IN c%u",
fsstate->cursor_number);
}
else
{
/* Easy: just rescan what we already have in memory, if anything */
fsstate->next_tuple = 0;
return;
}
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexec(fsstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, true, sql);
PQclear(res);
/* Now force a fresh FETCH. */
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
}
/*
* postgresEndForeignScan
* Finish scanning foreign table and dispose objects used for this scan
*/
static void
postgresEndForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
/* if fsstate is NULL, we are in EXPLAIN; nothing to do */
if (fsstate == NULL)
return;
/* Close the cursor if open, to prevent accumulation of cursors */
if (fsstate->cursor_exists)
close_cursor(fsstate->conn, fsstate->cursor_number);
/* Release remote connection */
ReleaseConnection(fsstate->conn);
fsstate->conn = NULL;
/* MemoryContexts will be deleted automatically. */
}
/*
* postgresAddForeignUpdateTargets
* Add resjunk column(s) needed for update/delete on a foreign table
*/
static void
postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation)
{
Var *var;
const char *attrname;
TargetEntry *tle;
/*
* In postgres_fdw, what we need is the ctid, same as for a regular table.
*/
/* Make a Var representing the desired value */
var = makeVar(parsetree->resultRelation,
SelfItemPointerAttributeNumber,
TIDOID,
-1,
InvalidOid,
0);
/* Wrap it in a resjunk TLE with the right name ... */
attrname = "ctid";
tle = makeTargetEntry((Expr *) var,
list_length(parsetree->targetList) + 1,
pstrdup(attrname),
true);
/* ... and add it to the query's targetlist */
parsetree->targetList = lappend(parsetree->targetList, tle);
}
/*
* postgresPlanForeignModify
* Plan an insert/update/delete operation on a foreign table
*
* Note: currently, the plan tree generated for UPDATE/DELETE will always
* include a ForeignScan that retrieves ctids (using SELECT FOR UPDATE)
* and then the ModifyTable node will have to execute individual remote
* UPDATE/DELETE commands. If there are no local conditions or joins
* needed, it'd be better to let the scan node do UPDATE/DELETE RETURNING
* and then do nothing at ModifyTable. Room for future optimization ...
*/
static List *
postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index)
{
CmdType operation = plan->operation;
StringInfoData sql;
List *targetAttrs = NIL;
List *returningList = NIL;
initStringInfo(&sql);
/*
* Construct a list of the columns that are to be assigned during INSERT
* or UPDATE. We should transmit only these columns, for performance and
* to respect any DEFAULT values the remote side may have for other
* columns. (XXX this will need some re-thinking when we support default
* expressions for foreign tables.)
*/
if (operation == CMD_INSERT || operation == CMD_UPDATE)
{
RangeTblEntry *rte = planner_rt_fetch(resultRelation, root);
Bitmapset *tmpset = bms_copy(rte->modifiedCols);
AttrNumber col;
while ((col = bms_first_member(tmpset)) >= 0)
{
col += FirstLowInvalidHeapAttributeNumber;
if (col <= InvalidAttrNumber) /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
targetAttrs = lappend_int(targetAttrs, col);
}
}
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists)
returningList = (List *) list_nth(plan->returningLists, subplan_index);
/*
* Construct the SQL command string.
*/
switch (operation)
{
case CMD_INSERT:
deparseInsertSql(&sql, root, resultRelation,
targetAttrs, returningList);
break;
case CMD_UPDATE:
deparseUpdateSql(&sql, root, resultRelation,
targetAttrs, returningList);
break;
case CMD_DELETE:
deparseDeleteSql(&sql, root, resultRelation, returningList);
break;
default:
elog(ERROR, "unexpected operation: %d", (int) operation);
break;
}
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwModifyPrivateIndex, above.
*/
return list_make3(makeString(sql.data),
targetAttrs,
makeInteger((returningList != NIL)));
}
/*
* postgresBeginForeignModify
* Begin an insert/update/delete operation on a foreign table
*/
static void
postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags)
{
PgFdwModifyState *fmstate;
EState *estate = mtstate->ps.state;
CmdType operation = mtstate->operation;
Relation rel = resultRelInfo->ri_RelationDesc;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
AttrNumber n_params;
Oid typefnoid;
bool isvarlena;
ListCell *lc;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. resultRelInfo->ri_FdwState
* stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/* Begin constructing PgFdwModifyState. */
fmstate = (PgFdwModifyState *) palloc0(sizeof(PgFdwModifyState));
fmstate->rel = rel;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
rte = rt_fetch(resultRelInfo->ri_RangeTableIndex, estate->es_range_table);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
table = GetForeignTable(RelationGetRelid(rel));
server = GetForeignServer(table->serverid);
user = GetUserMapping(userid, server->serverid);
/* Open connection; report that we'll create a prepared statement. */
fmstate->conn = GetConnection(server, user, true);
fmstate->p_name = NULL; /* prepared statement not made yet */
/* Deconstruct fdw_private data. */
fmstate->query = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
fmstate->target_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateTargetAttnums);
fmstate->has_returning = intVal(list_nth(fdw_private,
FdwModifyPrivateHasReturning));
/* Create context for per-tuple temp workspace. */
fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/* Prepare for input conversion of RETURNING results. */
if (fmstate->has_returning)
fmstate->attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(rel));
/* Prepare for output conversion of parameters used in prepared stmt. */
n_params = list_length(fmstate->target_attrs) + 1;
fmstate->p_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * n_params);
fmstate->p_nums = 0;
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
/* Find the ctid resjunk column in the subplan's result */
Plan *subplan = mtstate->mt_plans[subplan_index]->plan;
fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist,
"ctid");
if (!AttributeNumberIsValid(fmstate->ctidAttno))
elog(ERROR, "could not find junk ctid column");
/* First transmittable parameter will be ctid */
getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
if (operation == CMD_INSERT || operation == CMD_UPDATE)
{
/* Set up for remaining transmittable parameters */
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Form_pg_attribute attr = RelationGetDescr(rel)->attrs[attnum - 1];
Assert(!attr->attisdropped);
getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
}
Assert(fmstate->p_nums <= n_params);
resultRelInfo->ri_FdwState = fmstate;
}
/*
* postgresExecForeignInsert
* Insert one row into a foreign table
*/
static TupleTableSlot *
postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
const char **p_values;
PGresult *res;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate, NULL, slot);
/*
* Execute the prepared statement, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was inserted on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresExecForeignUpdate
* Update one row in a foreign table
*/
static TupleTableSlot *
postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
Datum datum;
bool isNull;
const char **p_values;
PGresult *res;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/* Get the ctid that was passed up as a resjunk column */
datum = ExecGetJunkAttribute(planSlot,
fmstate->ctidAttno,
&isNull);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate,
(ItemPointer) DatumGetPointer(datum),
slot);
/*
* Execute the prepared statement, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was updated on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresExecForeignDelete
* Delete one row from a foreign table
*/
static TupleTableSlot *
postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
Datum datum;
bool isNull;
const char **p_values;
PGresult *res;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/* Get the ctid that was passed up as a resjunk column */
datum = ExecGetJunkAttribute(planSlot,
fmstate->ctidAttno,
&isNull);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate,
(ItemPointer) DatumGetPointer(datum),
NULL);
/*
* Execute the prepared statement, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was deleted on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresEndForeignModify
* Finish an insert/update/delete operation on a foreign table
*/
static void
postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
/* If fmstate is NULL, we are in EXPLAIN; nothing to do */
if (fmstate == NULL)
return;
/* If we created a prepared statement, destroy it */
if (fmstate->p_name)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "DEALLOCATE %s", fmstate->p_name);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexec(fmstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, true, sql);
PQclear(res);
fmstate->p_name = NULL;
}
/* Release remote connection */
ReleaseConnection(fmstate->conn);
fmstate->conn = NULL;
}
/*
* postgresExplainForeignScan
* Produce extra output for EXPLAIN of a ForeignScan on a foreign table
*/
static void
postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
List *fdw_private;
char *sql;
if (es->verbose)
{
fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainForeignModify
* Produce extra output for EXPLAIN of a ModifyTable on a foreign table
*/
static void
postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es)
{
if (es->verbose)
{
char *sql = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* Estimate costs of executing given SQL statement.
*/
static void
get_remote_estimate(const char *sql, PGconn *conn,
double *rows, int *width,
Cost *startup_cost, Cost *total_cost)
{
PGresult *volatile res = NULL;
/* PGresult must be released before leaving this function. */
PG_TRY();
{
StringInfoData buf;
char *line;
char *p;
int n;
/*
* Execute EXPLAIN remotely on given SQL statement.
*/
initStringInfo(&buf);
appendStringInfo(&buf, "EXPLAIN %s", sql);
res = PQexec(conn, buf.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, false, buf.data);
/*
* Extract cost numbers for topmost plan node. Note we search for a
* left paren from the end of the line to avoid being confused by
* other uses of parentheses.
*/
line = PQgetvalue(res, 0, 0);
p = strrchr(line, '(');
if (p == NULL)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
n = sscanf(p, "(cost=%lf..%lf rows=%lf width=%d)",
startup_cost, total_cost, rows, width);
if (n != 4)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Create cursor for node's query with current parameter values.
*/
static void
create_cursor(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
int numParams = fsstate->numParams;
Oid *types = fsstate->param_types;
const char **values = fsstate->param_values;
PGconn *conn = fsstate->conn;
char *sql;
StringInfoData buf;
PGresult *res;
/*
* Construct array of external parameter values in text format. Since
* there might be random unconvertible stuff in the ParamExternData array,
* take care to convert only values we actually need.
*
* Note that we leak the memory for the value strings until end of query;
* this doesn't seem like a big problem, and in any case we might need to
* recreate the cursor after a rescan, so we could need to re-use the
* values anyway.
*/
if (numParams > 0 && !fsstate->extparams_done)
{
ParamListInfo params = node->ss.ps.state->es_param_list_info;
List *param_numbers;
ListCell *lc;
param_numbers = (List *)
list_nth(fsstate->fdw_private, FdwScanPrivateExternParamIds);
foreach(lc, param_numbers)
{
int paramno = lfirst_int(lc);
ParamExternData *prm = &params->params[paramno - 1];
/* give hook a chance in case parameter is dynamic */
if (!OidIsValid(prm->ptype) && params->paramFetch != NULL)
params->paramFetch(params, paramno);
/*
* Force the remote server to infer a type for this parameter.
* Since we explicitly cast every parameter (see deparse.c), the
* "inference" is trivial and will produce the desired result.
* This allows us to avoid assuming that the remote server has the
* same OIDs we do for the parameters' types.
*
* We'd not need to pass a type array to PQexecParams at all,
* except that there may be unused holes in the array, which will
* have to be filled with something or the remote server will
* complain. We arbitrarily set them to INT4OID earlier.
*/
types[paramno - 1] = InvalidOid;
/*
* Get string representation of each parameter value by invoking
* type-specific output function, unless the value is null.
*/
if (prm->isnull)
values[paramno - 1] = NULL;
else
{
Oid out_func;
bool isvarlena;
getTypeOutputInfo(prm->ptype, &out_func, &isvarlena);
values[paramno - 1] = OidOutputFunctionCall(out_func,
prm->value);
}
}
fsstate->extparams_done = true;
}
/* Construct the DECLARE CURSOR command */
sql = strVal(list_nth(fsstate->fdw_private, FdwScanPrivateSelectSql));
initStringInfo(&buf);
appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s",
fsstate->cursor_number, sql);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecParams(conn, buf.data, numParams, types, values,
NULL, NULL, 0);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, true, sql);
PQclear(res);
/* Mark the cursor as created, and show no tuples have been retrieved */
fsstate->cursor_exists = true;
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
/* Clean up */
pfree(buf.data);
}
/*
* Fetch some more rows from the node's cursor.
*/
static void
fetch_more_data(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
PGresult *volatile res = NULL;
MemoryContext oldcontext;
/*
* We'll store the tuples in the batch_cxt. First, flush the previous
* batch.
*/
fsstate->tuples = NULL;
MemoryContextReset(fsstate->batch_cxt);
oldcontext = MemoryContextSwitchTo(fsstate->batch_cxt);
/* PGresult must be released before leaving this function. */
PG_TRY();
{
PGconn *conn = fsstate->conn;
char sql[64];
int fetch_size;
int numrows;
int i;
/* The fetch size is arbitrary, but shouldn't be enormous. */
fetch_size = 100;
snprintf(sql, sizeof(sql), "FETCH %d FROM c%u",
fetch_size, fsstate->cursor_number);
res = PQexec(conn, sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, false,
strVal(list_nth(fsstate->fdw_private,
FdwScanPrivateSelectSql)));
/* Convert the data into HeapTuples */
numrows = PQntuples(res);
fsstate->tuples = (HeapTuple *) palloc0(numrows * sizeof(HeapTuple));
fsstate->num_tuples = numrows;
fsstate->next_tuple = 0;
for (i = 0; i < numrows; i++)
{
fsstate->tuples[i] =
make_tuple_from_result_row(res, i,
fsstate->rel,
fsstate->attinmeta,
fsstate->temp_cxt);
}
/* Update fetch_ct_2 */
if (fsstate->fetch_ct_2 < 2)
fsstate->fetch_ct_2++;
/* Must be EOF if we didn't get as many tuples as we asked for. */
fsstate->eof_reached = (numrows < fetch_size);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcontext);
}
/*
* Utility routine to close a cursor.
*/
static void
close_cursor(PGconn *conn, unsigned int cursor_number)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "CLOSE c%u", cursor_number);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexec(conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, true, sql);
PQclear(res);
}
/*
* prepare_foreign_modify
* Establish a prepared statement for execution of INSERT/UPDATE/DELETE
*/
static void
prepare_foreign_modify(PgFdwModifyState *fmstate)
{
char prep_name[NAMEDATALEN];
char *p_name;
PGresult *res;
/* Construct name we'll use for the prepared statement. */
snprintf(prep_name, sizeof(prep_name), "pgsql_fdw_prep_%u",
GetPrepStmtNumber(fmstate->conn));
p_name = pstrdup(prep_name);
/*
* We intentionally do not specify parameter types here, but leave the
* remote server to derive them by default. This avoids possible problems
* with the remote server using different type OIDs than we do. All of
* the prepared statements we use in this module are simple enough that
* the remote server will make the right choices.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQprepare(fmstate->conn,
p_name,
fmstate->query,
0,
NULL);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, true, fmstate->query);
PQclear(res);
/* This action shows that the prepare has been done. */
fmstate->p_name = p_name;
}
/*
* convert_prep_stmt_params
* Create array of text strings representing parameter values
*
* tupleid is ctid to send, or NULL if none
* slot is slot to get remaining parameters from, or NULL if none
*
* Data is constructed in temp_cxt; caller should reset that after use.
*/
static const char **
convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot)
{
const char **p_values;
int pindex = 0;
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(fmstate->temp_cxt);
p_values = (const char **) palloc(sizeof(char *) * fmstate->p_nums);
/* 1st parameter should be ctid, if it's in use */
if (tupleid != NULL)
{
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
PointerGetDatum(tupleid));
pindex++;
}
/* get following parameters from slot */
if (slot != NULL)
{
ListCell *lc;
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Datum value;
bool isnull;
value = slot_getattr(slot, attnum, &isnull);
if (isnull)
p_values[pindex] = NULL;
else
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
value);
pindex++;
}
}
Assert(pindex == fmstate->p_nums);
MemoryContextSwitchTo(oldcontext);
return p_values;
}
/*
* store_returning_result
* Store the result of a RETURNING clause
*
* On error, be sure to release the PGresult on the way out. Callers do not
* have PG_TRY blocks to ensure this happens.
*/
static void
store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res)
{
/* PGresult must be released before leaving this function. */
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(res, 0,
fmstate->rel,
fmstate->attinmeta,
fmstate->temp_cxt);
/* tuple will be deleted when it is cleared from the slot */
ExecStoreTuple(newtup, slot, InvalidBuffer, true);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* postgresAnalyzeForeignTable
* Test whether analyzing this foreign table is supported
*/
static bool
postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages)
{
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
PGconn *conn;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Return the row-analysis function pointer */
*func = postgresAcquireSampleRowsFunc;
/*
* Now we have to get the number of pages. It's annoying that the ANALYZE
* API requires us to return that now, because it forces some duplication
* of effort between this routine and postgresAcquireSampleRowsFunc. But
* it's probably not worth redefining that API at this point.
*/
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
server = GetForeignServer(table->serverid);
user = GetUserMapping(relation->rd_rel->relowner, server->serverid);
conn = GetConnection(server, user, false);
/*
* Construct command to get page count for relation.
*/
initStringInfo(&sql);
deparseAnalyzeSizeSql(&sql, relation);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = PQexec(conn, sql.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, false, sql.data);
if (PQntuples(res) != 1 || PQnfields(res) != 1)
elog(ERROR, "unexpected result from deparseAnalyzeSizeSql query");
*totalpages = strtoul(PQgetvalue(res, 0, 0), NULL, 10);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return true;
}
/*
* Acquire a random sample of rows from foreign table managed by postgres_fdw.
*
* We fetch the whole table from the remote side and pick out some sample rows.
*
* Selected rows are returned in the caller-allocated array rows[],
* which must have at least targrows entries.
* The actual number of rows selected is returned as the function result.
* We also count the total number of rows in the table and return it into
* *totalrows. Note that *totaldeadrows is always set to 0.
*
* Note that the returned list of rows is not always in order by physical
* position in the table. Therefore, correlation estimates derived later
* may be meaningless, but it's OK because we don't use the estimates
* currently (the planner only pays attention to correlation for indexscans).
*/
static int
postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows)
{
PgFdwAnalyzeState astate;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
PGconn *conn;
unsigned int cursor_number;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Initialize workspace state */
astate.rel = relation;
astate.attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(relation));
astate.rows = rows;
astate.targrows = targrows;
astate.numrows = 0;
astate.samplerows = 0;
astate.rowstoskip = -1; /* -1 means not set yet */
astate.rstate = anl_init_selection_state(targrows);
/* Remember ANALYZE context, and create a per-tuple temp context */
astate.anl_cxt = CurrentMemoryContext;
astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
server = GetForeignServer(table->serverid);
user = GetUserMapping(relation->rd_rel->relowner, server->serverid);
conn = GetConnection(server, user, false);
/*
* Construct cursor that retrieves whole rows from remote.
*/
cursor_number = GetCursorNumber(conn);
initStringInfo(&sql);
appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number);
deparseAnalyzeSql(&sql, relation);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = PQexec(conn, sql.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, false, sql.data);
PQclear(res);
res = NULL;
/* Retrieve and process rows a batch at a time. */
for (;;)
{
char fetch_sql[64];
int fetch_size;
int numrows;
int i;
/* Allow users to cancel long query */
CHECK_FOR_INTERRUPTS();
/*
* XXX possible future improvement: if rowstoskip is large, we
* could issue a MOVE rather than physically fetching the rows,
* then just adjust rowstoskip and samplerows appropriately.
*/
/* The fetch size is arbitrary, but shouldn't be enormous. */
fetch_size = 100;
/* Fetch some rows */
snprintf(fetch_sql, sizeof(fetch_sql), "FETCH %d FROM c%u",
fetch_size, cursor_number);
res = PQexec(conn, fetch_sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, false, sql.data);
/* Process whatever we got. */
numrows = PQntuples(res);
for (i = 0; i < numrows; i++)
analyze_row_processor(res, i, &astate);
PQclear(res);
res = NULL;
/* Must be EOF if we didn't get all the rows requested. */
if (numrows < fetch_size)
break;
}
/* Close the cursor, just to be tidy. */
close_cursor(conn, cursor_number);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
/* We assume that we have no dead tuple. */
*totaldeadrows = 0.0;
/* We've retrieved all living tuples from foreign server. */
*totalrows = astate.samplerows;
/*
* Emit some interesting relation info
*/
ereport(elevel,
(errmsg("\"%s\": table contains %.0f rows, %d rows in sample",
RelationGetRelationName(relation),
astate.samplerows, astate.numrows)));
return astate.numrows;
}
/*
* Collect sample rows from the result of query.
* - Use all tuples in sample until target # of samples are collected.
* - Subsequently, replace already-sampled tuples randomly.
*/
static void
analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
{
int targrows = astate->targrows;
int pos; /* array index to store tuple in */
MemoryContext oldcontext;
/* Always increment sample row counter. */
astate->samplerows += 1;
/*
* Determine the slot where this sample row should be stored. Set pos to
* negative value to indicate the row should be skipped.
*/
if (astate->numrows < targrows)
{
/* First targrows rows are always included into the sample */
pos = astate->numrows++;
}
else
{
/*
* Now we start replacing tuples in the sample until we reach the end
* of the relation. Same algorithm as in acquire_sample_rows in
* analyze.c; see Jeff Vitter's paper.
*/
if (astate->rowstoskip < 0)
astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
&astate->rstate);
if (astate->rowstoskip <= 0)
{
/* Choose a random reservoir element to replace. */
pos = (int) (targrows * anl_random_fract());
Assert(pos >= 0 && pos < targrows);
heap_freetuple(astate->rows[pos]);
}
else
{
/* Skip this tuple. */
pos = -1;
}
astate->rowstoskip -= 1;
}
if (pos >= 0)
{
/*
* Create sample tuple from current result row, and store it in the
* position determined above. The tuple has to be created in anl_cxt.
*/
oldcontext = MemoryContextSwitchTo(astate->anl_cxt);
astate->rows[pos] = make_tuple_from_result_row(res, row,
astate->rel,
astate->attinmeta,
astate->temp_cxt);
MemoryContextSwitchTo(oldcontext);
}
}
/*
* Create a tuple from the specified row of the PGresult.
*
* rel is the local representation of the foreign table, attinmeta is
* conversion data for the rel's tupdesc, and temp_context is a working
* context that can be reset after each tuple.
*/
static HeapTuple
make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
MemoryContext temp_context)
{
HeapTuple tuple;
TupleDesc tupdesc = RelationGetDescr(rel);
Form_pg_attribute *attrs = tupdesc->attrs;
Datum *values;
bool *nulls;
ItemPointer ctid = NULL;
ConversionLocation errpos;
ErrorContextCallback errcallback;
MemoryContext oldcontext;
int i;
int j;
Assert(row < PQntuples(res));
/*
* Do the following work in a temp context that we reset after each tuple.
* This cleans up not only the data we have direct access to, but any
* cruft the I/O functions might leak.
*/
oldcontext = MemoryContextSwitchTo(temp_context);
values = (Datum *) palloc(tupdesc->natts * sizeof(Datum));
nulls = (bool *) palloc(tupdesc->natts * sizeof(bool));
/*
* Set up and install callback to report where conversion error occurs.
*/
errpos.rel = rel;
errpos.cur_attno = 0;
errcallback.callback = conversion_error_callback;
errcallback.arg = (void *) &errpos;
errcallback.previous = error_context_stack;
error_context_stack = &errcallback;
/*
* i indexes columns in the relation, j indexes columns in the PGresult.
* We assume dropped columns are not represented in the PGresult.
*/
for (i = 0, j = 0; i < tupdesc->natts; i++)
{
char *valstr;
/* skip dropped columns. */
if (attrs[i]->attisdropped)
{
values[i] = (Datum) 0;
nulls[i] = true;
continue;
}
/* convert value to internal representation */
if (PQgetisnull(res, row, j))
{
valstr = NULL;
nulls[i] = true;
}
else
{
valstr = PQgetvalue(res, row, j);
nulls[i] = false;
}
/* Note: apply the input function even to nulls, to support domains */
errpos.cur_attno = i + 1;
values[i] = InputFunctionCall(&attinmeta->attinfuncs[i],
valstr,
attinmeta->attioparams[i],
attinmeta->atttypmods[i]);
errpos.cur_attno = 0;
j++;
}
/*
* Convert ctid if present. XXX we could stand to have a cleaner way of
* detecting whether ctid is included in the result.
*/
if (j < PQnfields(res))
{
char *valstr;
Datum datum;
valstr = PQgetvalue(res, row, j);
datum = DirectFunctionCall1(tidin, CStringGetDatum(valstr));
ctid = (ItemPointer) DatumGetPointer(datum);
j++;
}
/* Uninstall error context callback. */
error_context_stack = errcallback.previous;
/* check result and tuple descriptor have the same number of columns */
if (j != PQnfields(res))
elog(ERROR, "remote query result does not match the foreign table");
/*
* Build the result tuple in caller's memory context.
*/
MemoryContextSwitchTo(oldcontext);
tuple = heap_form_tuple(tupdesc, values, nulls);
if (ctid)
tuple->t_self = *ctid;
/* Clean up */
MemoryContextReset(temp_context);
return tuple;
}
/*
* Callback function which is called when error occurs during column value
* conversion. Print names of column and relation.
*/
static void
conversion_error_callback(void *arg)
{
ConversionLocation *errpos = (ConversionLocation *) arg;
TupleDesc tupdesc = RelationGetDescr(errpos->rel);
if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts)
errcontext("column \"%s\" of foreign table \"%s\"",
NameStr(tupdesc->attrs[errpos->cur_attno - 1]->attname),
RelationGetRelationName(errpos->rel));
}