nodeSubqueryscan.c

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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) 1996-2025, 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/executor.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)
{
    /*
     * 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);
}