nodeCustom.c

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/* ------------------------------------------------------------------------
 *
 * nodeCustom.c
 *      Routines to handle execution of custom scan node
 *
 * Portions Copyright (c) 1996-2016, 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 "nodes/execnodes.h"
#include "nodes/plannodes.h"
#include "parser/parsetree.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "utils/rel.h"

CustomScanState *
ExecInitCustomScan(CustomScan *cscan, EState *estate, int eflags)
{
    CustomScanState *css;
    Relation    scan_rel = NULL;
    Index       scanrelid = cscan->scan.scanrelid;
    Index       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 = (CustomScanState *) cscan->methods->CreateCustomScanState(cscan);
    Assert(IsA(css, CustomScanState));

    /* 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;

    /* create expression context for node */
    ExecAssignExprContext(estate, &css->ss.ps);

    css->ss.ps.ps_TupFromTlist = false;

    /* initialize child expressions */
    css->ss.ps.targetlist = (List *)
        ExecInitExpr((Expr *) cscan->scan.plan.targetlist,
                     (PlanState *) css);
    css->ss.ps.qual = (List *)
        ExecInitExpr((Expr *) cscan->scan.plan.qual,
                     (PlanState *) css);

    /* tuple table initialization */
    ExecInitScanTupleSlot(estate, &css->ss);
    ExecInitResultTupleSlot(estate, &css->ss.ps);

    /*
     * open the base relation, if any, and acquire an appropriate lock on it
     */
    if (scanrelid > 0)
    {
        scan_rel = ExecOpenScanRelation(estate, scanrelid, eflags);
        css->ss.ss_currentRelation = scan_rel;
    }

    /*
     * 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, false);
        ExecAssignScanType(&css->ss, scan_tupdesc);
        /* Node's targetlist will contain Vars with varno = INDEX_VAR */
        tlistvarno = INDEX_VAR;
    }
    else
    {
        ExecAssignScanType(&css->ss, RelationGetDescr(scan_rel));
        /* Node's targetlist will contain Vars with varno = scanrelid */
        tlistvarno = scanrelid;
    }

    /*
     * Initialize result tuple type and projection info.
     */
    ExecAssignResultTypeFromTL(&css->ss.ps);
    ExecAssignScanProjectionInfoWithVarno(&css->ss, tlistvarno);

    /*
     * 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;
}

TupleTableSlot *
ExecCustomScan(CustomScanState *node)
{
    Assert(node->methods->ExecCustomScan != NULL);
    return node->methods->ExecCustomScan(node);
}

void
ExecEndCustomScan(CustomScanState *node)
{
    Assert(node->methods->EndCustomScan != NULL);
    node->methods->EndCustomScan(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 heap relation */
    if (node->ss.ss_currentRelation)
        ExecCloseScanRelation(node->ss.ss_currentRelation);
}

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
ExecCustomScanInitializeWorker(CustomScanState *node, shm_toc *toc)
{
    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(toc, plan_node_id);
        methods->InitializeWorkerCustomScan(node, toc, coordinate);
    }
}