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nodeForeignscan.c
nodeForeignscan.c 9.74 KiB
/*-------------------------------------------------------------------------
*
* nodeForeignscan.c
* Routines to support scans of foreign tables
*
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeForeignscan.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
*
* ExecForeignScan scans a foreign table.
* ExecInitForeignScan creates and initializes state info.
* ExecReScanForeignScan rescans the foreign relation.
* ExecEndForeignScan releases any resources allocated.
*/
#include "postgres.h"
#include "executor/executor.h"
#include "executor/nodeForeignscan.h"
#include "foreign/fdwapi.h"
#include "utils/memutils.h"
#include "utils/rel.h"
static TupleTableSlot *ForeignNext(ForeignScanState *node);
static bool ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot);
/* ----------------------------------------------------------------
* ForeignNext
*
* This is a workhorse for ExecForeignScan
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ForeignNext(ForeignScanState *node)
{
TupleTableSlot *slot;
ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
MemoryContext oldcontext;
/* Call the Iterate function in short-lived context */
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
slot = node->fdwroutine->IterateForeignScan(node);
MemoryContextSwitchTo(oldcontext);
/*
* If any system columns are requested, we have to force the tuple into
* physical-tuple form to avoid "cannot extract system attribute from
* virtual tuple" errors later. We also insert a valid value for
* tableoid, which is the only actually-useful system column.
*/
if (plan->fsSystemCol && !TupIsNull(slot))
{
HeapTuple tup = ExecMaterializeSlot(slot);
tup->t_tableOid = RelationGetRelid(node->ss.ss_currentRelation);
}
return slot;
}
/* * ForeignRecheck -- access method routine to recheck a tuple in EvalPlanQual
*/
static bool
ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot)
{
FdwRoutine *fdwroutine = node->fdwroutine;
ExprContext *econtext;
/*
* extract necessary information from foreign scan node
*/
econtext = node->ss.ps.ps_ExprContext;
/* Does the tuple meet the remote qual condition? */
econtext->ecxt_scantuple = slot;
ResetExprContext(econtext);
/*
* If an outer join is pushed down, RecheckForeignScan may need to store a
* different tuple in the slot, because a different set of columns may go
* to NULL upon recheck. Otherwise, it shouldn't need to change the slot
* contents, just return true or false to indicate whether the quals still
* pass. For simple cases, setting fdw_recheck_quals may be easier than
* providing this callback.
*/
if (fdwroutine->RecheckForeignScan &&
!fdwroutine->RecheckForeignScan(node, slot))
return false;
return ExecQual(node->fdw_recheck_quals, econtext, false);
}
/* ----------------------------------------------------------------
* ExecForeignScan(node)
*
* Fetches the next tuple from the FDW, checks local quals, and
* returns it.
* We call the ExecScan() routine and pass it the appropriate
* access method functions.
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecForeignScan(ForeignScanState *node)
{
return ExecScan((ScanState *) node,
(ExecScanAccessMtd) ForeignNext,
(ExecScanRecheckMtd) ForeignRecheck);
}
/* ----------------------------------------------------------------
* ExecInitForeignScan
* ----------------------------------------------------------------
*/
ForeignScanState *
ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags)
{
ForeignScanState *scanstate;
Relation currentRelation = NULL;
Index scanrelid = node->scan.scanrelid;
Index tlistvarno;
FdwRoutine *fdwroutine;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* create state structure
*/ scanstate = makeNode(ForeignScanState);
scanstate->ss.ps.plan = (Plan *) node;
scanstate->ss.ps.state = estate;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &scanstate->ss.ps);
scanstate->ss.ps.ps_TupFromTlist = false;
/*
* initialize child expressions
*/
scanstate->ss.ps.targetlist = (List *)
ExecInitExpr((Expr *) node->scan.plan.targetlist,
(PlanState *) scanstate);
scanstate->ss.ps.qual = (List *)
ExecInitExpr((Expr *) node->scan.plan.qual,
(PlanState *) scanstate);
scanstate->fdw_recheck_quals = (List *)
ExecInitExpr((Expr *) node->fdw_recheck_quals,
(PlanState *) scanstate);
/*
* tuple table initialization
*/
ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
ExecInitScanTupleSlot(estate, &scanstate->ss);
/*
* open the base relation, if any, and acquire an appropriate lock on it;
* also acquire function pointers from the FDW's handler
*/
if (scanrelid > 0)
{
currentRelation = ExecOpenScanRelation(estate, scanrelid, eflags);
scanstate->ss.ss_currentRelation = currentRelation;
fdwroutine = GetFdwRoutineForRelation(currentRelation, true);
}
else
{
/* We can't use the relcache, so get fdwroutine the hard way */
fdwroutine = GetFdwRoutineByServerId(node->fs_server);
}
/*
* Determine the scan tuple type. If the FDW provided a targetlist
* describing the scan tuples, use that; else use base relation's rowtype.
*/
if (node->fdw_scan_tlist != NIL || currentRelation == NULL)
{
TupleDesc scan_tupdesc;
scan_tupdesc = ExecTypeFromTL(node->fdw_scan_tlist, false);
ExecAssignScanType(&scanstate->ss, scan_tupdesc);
/* Node's targetlist will contain Vars with varno = INDEX_VAR */
tlistvarno = INDEX_VAR;
}
else
{
ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation));
/* Node's targetlist will contain Vars with varno = scanrelid */
tlistvarno = scanrelid;
}
/*
* Initialize result tuple type and projection info. */
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
ExecAssignScanProjectionInfoWithVarno(&scanstate->ss, tlistvarno);
/*
* Initialize FDW-related state.
*/
scanstate->fdwroutine = fdwroutine;
scanstate->fdw_state = NULL;
/* Initialize any outer plan. */
if (outerPlan(node))
outerPlanState(scanstate) =
ExecInitNode(outerPlan(node), estate, eflags);
/*
* Tell the FDW to initialize the scan.
*/
fdwroutine->BeginForeignScan(scanstate, eflags);
return scanstate;
}
/* ----------------------------------------------------------------
* ExecEndForeignScan
*
* frees any storage allocated through C routines.
* ----------------------------------------------------------------
*/
void
ExecEndForeignScan(ForeignScanState *node)
{
/* Let the FDW shut down */
node->fdwroutine->EndForeignScan(node);
/* Shut down any outer plan. */
if (outerPlanState(node))
ExecEndNode(outerPlanState(node));
/* Free the exprcontext */
ExecFreeExprContext(&node->ss.ps);
/* clean out the tuple table */
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
ExecClearTuple(node->ss.ss_ScanTupleSlot);
/* close the relation. */
if (node->ss.ss_currentRelation)
ExecCloseScanRelation(node->ss.ss_currentRelation);
}
/* ----------------------------------------------------------------
* ExecReScanForeignScan
*
* Rescans the relation.
* ----------------------------------------------------------------
*/
void
ExecReScanForeignScan(ForeignScanState *node)
{
PlanState *outerPlan = outerPlanState(node);
node->fdwroutine->ReScanForeignScan(node);
/*
* If chgParam of subnode is not null then plan will be re-scanned by
* first ExecProcNode. outerPlan may also be NULL, in which case there
* is nothing to rescan at all.
*/
if (outerPlan != NULL && outerPlan->chgParam == NULL) ExecReScan(outerPlan);
ExecScanReScan(&node->ss);
}
/* ----------------------------------------------------------------
* ExecForeignScanEstimate
*
* Informs size of the parallel coordination information, if any
* ----------------------------------------------------------------
*/
void
ExecForeignScanEstimate(ForeignScanState *node, ParallelContext *pcxt)
{
FdwRoutine *fdwroutine = node->fdwroutine;
if (fdwroutine->EstimateDSMForeignScan)
{
node->pscan_len = fdwroutine->EstimateDSMForeignScan(node, pcxt);
shm_toc_estimate_chunk(&pcxt->estimator, node->pscan_len);
shm_toc_estimate_keys(&pcxt->estimator, 1);
}
}
/* ----------------------------------------------------------------
* ExecForeignScanInitializeDSM
*
* Initialize the parallel coordination information
* ----------------------------------------------------------------
*/
void
ExecForeignScanInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
{
FdwRoutine *fdwroutine = node->fdwroutine;
if (fdwroutine->InitializeDSMForeignScan)
{
int plan_node_id = node->ss.ps.plan->plan_node_id;
void *coordinate;
coordinate = shm_toc_allocate(pcxt->toc, node->pscan_len);
fdwroutine->InitializeDSMForeignScan(node, pcxt, coordinate);
shm_toc_insert(pcxt->toc, plan_node_id, coordinate);
}
}
/* ----------------------------------------------------------------
* ExecForeignScanInitializeDSM
*
* Initialization according to the parallel coordination information
* ----------------------------------------------------------------
*/
void
ExecForeignScanInitializeWorker(ForeignScanState *node, shm_toc *toc)
{
FdwRoutine *fdwroutine = node->fdwroutine;
if (fdwroutine->InitializeWorkerForeignScan)
{
int plan_node_id = node->ss.ps.plan->plan_node_id;
void *coordinate;
coordinate = shm_toc_lookup(toc, plan_node_id);
fdwroutine->InitializeWorkerForeignScan(node, toc, coordinate);
}
}