nodeCustom.c

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/* ------------------------------------------------------------------------
 *
 * nodeCustom.c
 *      Routines to handle execution of custom scan node
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * ------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/parallel.h"
#include "executor/executor.h"
#include "executor/nodeCustom.h"
#include "miscadmin.h"
#include "nodes/execnodes.h"
#include "nodes/extensible.h"
#include "nodes/plannodes.h"
#include "utils/rel.h"
 
static TupleTableSlot *ExecCustomScan(PlanState *pstate);
 
 
CustomScanState *
ExecInitCustomScan(CustomScan *cscan, EState *estate, int eflags)
{
    CustomScanState *css;
    const TupleTableSlotOps *slotOps;
    Relation    scan_rel = NULL;
    Index       scanrelid = cscan->scan.scanrelid;
    int         tlistvarno;
 
    /*
     * Allocate the CustomScanState object.  We let the custom scan provider
     * do the palloc, in case it wants to make a larger object that embeds
     * CustomScanState as the first field.  It must set the node tag and the
     * methods field correctly at this time.  Other standard fields should be
     * set to zero.
     */
    css = castNode(CustomScanState,
                   cscan->methods->CreateCustomScanState(cscan));
 
    /* ensure flags is filled correctly */
    css->flags = cscan->flags;
 
    /* fill up fields of ScanState */
    css->ss.ps.plan = &cscan->scan.plan;
    css->ss.ps.state = estate;
    css->ss.ps.ExecProcNode = ExecCustomScan;
 
    /* create expression context for node */
    ExecAssignExprContext(estate, &css->ss.ps);
 
    /*
     * open the scan relation, if any
     */
    if (scanrelid > 0)
    {
        scan_rel = ExecOpenScanRelation(estate, scanrelid, eflags);
        css->ss.ss_currentRelation = scan_rel;
    }
 
    /*
     * Use a custom slot if specified in CustomScanState or use virtual slot
     * otherwise.
     */
    slotOps = css->slotOps;
    if (!slotOps)
        slotOps = &TTSOpsVirtual;
 
    /*
     * Determine the scan tuple type.  If the custom scan provider provided a
     * targetlist describing the scan tuples, use that; else use base
     * relation's rowtype.
     */
    if (cscan->custom_scan_tlist != NIL || scan_rel == NULL)
    {
        TupleDesc   scan_tupdesc;
 
        scan_tupdesc = ExecTypeFromTL(cscan->custom_scan_tlist);
        ExecInitScanTupleSlot(estate, &css->ss, scan_tupdesc, slotOps);
        /* Node's targetlist will contain Vars with varno = INDEX_VAR */
        tlistvarno = INDEX_VAR;
    }
    else
    {
        ExecInitScanTupleSlot(estate, &css->ss, RelationGetDescr(scan_rel),
                              slotOps);
        /* Node's targetlist will contain Vars with varno = scanrelid */
        tlistvarno = scanrelid;
    }
 
    /*
     * Initialize result slot, type and projection.
     */
    ExecInitResultTupleSlotTL(&css->ss.ps, &TTSOpsVirtual);
    ExecAssignScanProjectionInfoWithVarno(&css->ss, tlistvarno);
 
    /* initialize child expressions */
    css->ss.ps.qual =
        ExecInitQual(cscan->scan.plan.qual, (PlanState *) css);
 
    /*
     * The callback of custom-scan provider applies the final initialization
     * of the custom-scan-state node according to its logic.
     */
    css->methods->BeginCustomScan(css, estate, eflags);
 
    return css;
}
 
static TupleTableSlot *
ExecCustomScan(PlanState *pstate)
{
    CustomScanState *node = castNode(CustomScanState, pstate);
 
    CHECK_FOR_INTERRUPTS();
 
    Assert(node->methods->ExecCustomScan != NULL);
    return node->methods->ExecCustomScan(node);
}
 
void
ExecEndCustomScan(CustomScanState *node)
{
    Assert(node->methods->EndCustomScan != NULL);
    node->methods->EndCustomScan(node);
}
 
void
ExecReScanCustomScan(CustomScanState *node)
{
    Assert(node->methods->ReScanCustomScan != NULL);
    node->methods->ReScanCustomScan(node);
}
 
void
ExecCustomMarkPos(CustomScanState *node)
{
    if (!node->methods->MarkPosCustomScan)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("custom scan \"%s\" does not support MarkPos",
                        node->methods->CustomName)));
    node->methods->MarkPosCustomScan(node);
}
 
void
ExecCustomRestrPos(CustomScanState *node)
{
    if (!node->methods->RestrPosCustomScan)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("custom scan \"%s\" does not support MarkPos",
                        node->methods->CustomName)));
    node->methods->RestrPosCustomScan(node);
}
 
void
ExecCustomScanEstimate(CustomScanState *node, ParallelContext *pcxt)
{
    const CustomExecMethods *methods = node->methods;
 
    if (methods->EstimateDSMCustomScan)
    {
        node->pscan_len = methods->EstimateDSMCustomScan(node, pcxt);
        shm_toc_estimate_chunk(&pcxt->estimator, node->pscan_len);
        shm_toc_estimate_keys(&pcxt->estimator, 1);
    }
}
 
void
ExecCustomScanInitializeDSM(CustomScanState *node, ParallelContext *pcxt)
{
    const CustomExecMethods *methods = node->methods;
 
    if (methods->InitializeDSMCustomScan)
    {
        int         plan_node_id = node->ss.ps.plan->plan_node_id;
        void       *coordinate;
 
        coordinate = shm_toc_allocate(pcxt->toc, node->pscan_len);
        methods->InitializeDSMCustomScan(node, pcxt, coordinate);
        shm_toc_insert(pcxt->toc, plan_node_id, coordinate);
    }
}
 
void
ExecCustomScanReInitializeDSM(CustomScanState *node, ParallelContext *pcxt)
{
    const CustomExecMethods *methods = node->methods;
 
    if (methods->ReInitializeDSMCustomScan)
    {
        int         plan_node_id = node->ss.ps.plan->plan_node_id;
        void       *coordinate;
 
        coordinate = shm_toc_lookup(pcxt->toc, plan_node_id, false);
        methods->ReInitializeDSMCustomScan(node, pcxt, coordinate);
    }
}
 
void
ExecCustomScanInitializeWorker(CustomScanState *node,
                               ParallelWorkerContext *pwcxt)
{
    const CustomExecMethods *methods = node->methods;
 
    if (methods->InitializeWorkerCustomScan)
    {
        int         plan_node_id = node->ss.ps.plan->plan_node_id;
        void       *coordinate;
 
        coordinate = shm_toc_lookup(pwcxt->toc, plan_node_id, false);
        methods->InitializeWorkerCustomScan(node, pwcxt->toc, coordinate);
    }
}
 
void
ExecShutdownCustomScan(CustomScanState *node)
{
    const CustomExecMethods *methods = node->methods;
 
    if (methods->ShutdownCustomScan)
        methods->ShutdownCustomScan(node);
}