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/*-------------------------------------------------------------------------
*
* nodeSubqueryscan.c
* Support routines for scanning subqueries (subselects in rangetable).
*
* This is just enough different from sublinks (nodeSubplan.c) to mean that
* we need two sets of code. Ought to look at trying to unify the cases.
*
*
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeSubqueryscan.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* ExecSubqueryScan scans a subquery.
* ExecSubqueryNext retrieve next tuple in sequential order.
* ExecInitSubqueryScan creates and initializes a subqueryscan node.
* ExecEndSubqueryScan releases any storage allocated.
* ExecReScanSubqueryScan rescans the relation
*
*/
#include "postgres.h"
#include "executor/execdebug.h"
#include "executor/nodeSubqueryscan.h"
static TupleTableSlot *SubqueryNext(SubqueryScanState *node);
/* ----------------------------------------------------------------
* Scan Support
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* SubqueryNext
*
* This is a workhorse for ExecSubqueryScan
* ----------------------------------------------------------------
*/
static TupleTableSlot *
SubqueryNext(SubqueryScanState *node)
{
TupleTableSlot *slot;
/*
* Get the next tuple from the sub-query.
*/
slot = ExecProcNode(node->subplan);
/*
* We just return the subplan's result slot, rather than expending extra
* cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for
* EvalPlanQual rechecks.)
*/
return slot;
}
/*
* SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual
*/
static bool
SubqueryRecheck(SubqueryScanState *node, TupleTableSlot *slot)
{
/* nothing to check */
return true;
}
/* ----------------------------------------------------------------
* ExecSubqueryScan(node)
*
* Scans the subquery sequentially and returns the next qualifying
* tuple.
* We call the ExecScan() routine and pass it the appropriate
* access method functions.
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ExecSubqueryScan(PlanState *pstate)
{
SubqueryScanState *node = castNode(SubqueryScanState, pstate);
return ExecScan(&node->ss,
(ExecScanAccessMtd) SubqueryNext,
(ExecScanRecheckMtd) SubqueryRecheck);
}
/* ----------------------------------------------------------------
* ExecInitSubqueryScan
* ----------------------------------------------------------------
*/
SubqueryScanState *
ExecInitSubqueryScan(SubqueryScan *node, EState *estate, int eflags)
{
SubqueryScanState *subquerystate;
/* check for unsupported flags */
Assert(!(eflags & EXEC_FLAG_MARK));
/* SubqueryScan should not have any "normal" children */
Assert(outerPlan(node) == NULL);
Assert(innerPlan(node) == NULL);
/*
* create state structure
*/
subquerystate = makeNode(SubqueryScanState);
subquerystate->ss.ps.plan = (Plan *) node;
subquerystate->ss.ps.state = estate;
subquerystate->ss.ps.ExecProcNode = ExecSubqueryScan;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &subquerystate->ss.ps);
/*
* initialize subquery
*/
subquerystate->subplan = ExecInitNode(node->subplan, estate, eflags);
/*
* Initialize scan slot and type (needed by ExecAssignScanProjectionInfo)
*/
ExecInitScanTupleSlot(estate, &subquerystate->ss,
ExecGetResultType(subquerystate->subplan),
ExecGetResultSlotOps(subquerystate->subplan, NULL));
/*
* The slot used as the scantuple isn't the slot above (outside of EPQ),
* but the one from the node below.
*/
subquerystate->ss.ps.scanopsset = true;
subquerystate->ss.ps.scanops = ExecGetResultSlotOps(subquerystate->subplan,
&subquerystate->ss.ps.scanopsfixed);
subquerystate->ss.ps.resultopsset = true;
subquerystate->ss.ps.resultops = subquerystate->ss.ps.scanops;
subquerystate->ss.ps.resultopsfixed = subquerystate->ss.ps.scanopsfixed;
/*
* Initialize result type and projection.
*/
ExecInitResultTypeTL(&subquerystate->ss.ps);
ExecAssignScanProjectionInfo(&subquerystate->ss);
/*
* initialize child expressions
*/
subquerystate->ss.ps.qual =
ExecInitQual(node->scan.plan.qual, (PlanState *) subquerystate);
return subquerystate;
}
/* ----------------------------------------------------------------
* ExecEndSubqueryScan
*
* frees any storage allocated through C routines.
* ----------------------------------------------------------------
*/
void
ExecEndSubqueryScan(SubqueryScanState *node)
{
/*
* Free the exprcontext
*/
ExecFreeExprContext(&node->ss.ps);
/*
* clean out the upper tuple table
*/
if (node->ss.ps.ps_ResultTupleSlot)
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
ExecClearTuple(node->ss.ss_ScanTupleSlot);
/*
* close down subquery
*/
ExecEndNode(node->subplan);
}
/* ----------------------------------------------------------------
* ExecReScanSubqueryScan
*
* Rescans the relation.
* ----------------------------------------------------------------
*/
void
ExecReScanSubqueryScan(SubqueryScanState *node)
{
ExecScanReScan(&node->ss);
/*
* ExecReScan doesn't know about my subplan, so I have to do
* changed-parameter signaling myself. This is just as well, because the
* subplan has its own memory context in which its chgParam state lives.
*/
if (node->ss.ps.chgParam != NULL)
UpdateChangedParamSet(node->subplan, node->ss.ps.chgParam);
/*
* if chgParam of subnode is not null then plan will be re-scanned by
* first ExecProcNode.
*/
if (node->subplan->chgParam == NULL)
ExecReScan(node->subplan);
}
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