nodeBitmapIndexscan.c

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/*-------------------------------------------------------------------------
 *
 * nodeBitmapIndexscan.c
 *    Routines to support bitmapped index scans of relations
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/executor/nodeBitmapIndexscan.c
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *      MultiExecBitmapIndexScan    scans a relation using index.
 *      ExecInitBitmapIndexScan     creates and initializes state info.
 *      ExecReScanBitmapIndexScan   prepares to rescan the plan.
 *      ExecEndBitmapIndexScan      releases all storage.
 */
#include "postgres.h"
 
#include "access/genam.h"
#include "executor/executor.h"
#include "executor/nodeBitmapIndexscan.h"
#include "executor/nodeIndexscan.h"
#include "miscadmin.h"
 
 
/* ----------------------------------------------------------------
 *      ExecBitmapIndexScan
 *
 *      stub for pro forma compliance
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecBitmapIndexScan(PlanState *pstate)
{
    elog(ERROR, "BitmapIndexScan node does not support ExecProcNode call convention");
    return NULL;
}
 
/* ----------------------------------------------------------------
 *      MultiExecBitmapIndexScan(node)
 * ----------------------------------------------------------------
 */
Node *
MultiExecBitmapIndexScan(BitmapIndexScanState *node)
{
    TIDBitmap  *tbm;
    IndexScanDesc scandesc;
    double      nTuples = 0;
    bool        doscan;
 
    /* must provide our own instrumentation support */
    if (node->ss.ps.instrument)
        InstrStartNode(node->ss.ps.instrument);
 
    /*
     * extract necessary information from index scan node
     */
    scandesc = node->biss_ScanDesc;
 
    /*
     * If we have runtime keys and they've not already been set up, do it now.
     * Array keys are also treated as runtime keys; note that if ExecReScan
     * returns with biss_RuntimeKeysReady still false, then there is an empty
     * array key so we should do nothing.
     */
    if (!node->biss_RuntimeKeysReady &&
        (node->biss_NumRuntimeKeys != 0 || node->biss_NumArrayKeys != 0))
    {
        ExecReScan((PlanState *) node);
        doscan = node->biss_RuntimeKeysReady;
    }
    else
        doscan = true;
 
    /*
     * Prepare the result bitmap.  Normally we just create a new one to pass
     * back; however, our parent node is allowed to store a pre-made one into
     * node->biss_result, in which case we just OR our tuple IDs into the
     * existing bitmap.  (This saves needing explicit UNION steps.)
     */
    if (node->biss_result)
    {
        tbm = node->biss_result;
        node->biss_result = NULL;   /* reset for next time */
    }
    else
    {
        /* XXX should we use less than work_mem for this? */
        tbm = tbm_create(work_mem * (Size) 1024,
                         ((BitmapIndexScan *) node->ss.ps.plan)->isshared ?
                         node->ss.ps.state->es_query_dsa : NULL);
    }
 
    /*
     * Get TIDs from index and insert into bitmap
     */
    while (doscan)
    {
        nTuples += (double) index_getbitmap(scandesc, tbm);
 
        CHECK_FOR_INTERRUPTS();
 
        doscan = ExecIndexAdvanceArrayKeys(node->biss_ArrayKeys,
                                           node->biss_NumArrayKeys);
        if (doscan)             /* reset index scan */
            index_rescan(node->biss_ScanDesc,
                         node->biss_ScanKeys, node->biss_NumScanKeys,
                         NULL, 0);
    }
 
    /* must provide our own instrumentation support */
    if (node->ss.ps.instrument)
        InstrStopNode(node->ss.ps.instrument, nTuples);
 
    return (Node *) tbm;
}
 
/* ----------------------------------------------------------------
 *      ExecReScanBitmapIndexScan(node)
 *
 *      Recalculates the values of any scan keys whose value depends on
 *      information known at runtime, then rescans the indexed relation.
 * ----------------------------------------------------------------
 */
void
ExecReScanBitmapIndexScan(BitmapIndexScanState *node)
{
    ExprContext *econtext = node->biss_RuntimeContext;
 
    /*
     * Reset the runtime-key context so we don't leak memory as each outer
     * tuple is scanned.  Note this assumes that we will recalculate *all*
     * runtime keys on each call.
     */
    if (econtext)
        ResetExprContext(econtext);
 
    /*
     * If we are doing runtime key calculations (ie, any of the index key
     * values weren't simple Consts), compute the new key values.
     *
     * Array keys are also treated as runtime keys; note that if we return
     * with biss_RuntimeKeysReady still false, then there is an empty array
     * key so no index scan is needed.
     */
    if (node->biss_NumRuntimeKeys != 0)
        ExecIndexEvalRuntimeKeys(econtext,
                                 node->biss_RuntimeKeys,
                                 node->biss_NumRuntimeKeys);
    if (node->biss_NumArrayKeys != 0)
        node->biss_RuntimeKeysReady =
            ExecIndexEvalArrayKeys(econtext,
                                   node->biss_ArrayKeys,
                                   node->biss_NumArrayKeys);
    else
        node->biss_RuntimeKeysReady = true;
 
    /* reset index scan */
    if (node->biss_RuntimeKeysReady)
        index_rescan(node->biss_ScanDesc,
                     node->biss_ScanKeys, node->biss_NumScanKeys,
                     NULL, 0);
}
 
/* ----------------------------------------------------------------
 *      ExecEndBitmapIndexScan
 * ----------------------------------------------------------------
 */
void
ExecEndBitmapIndexScan(BitmapIndexScanState *node)
{
    Relation    indexRelationDesc;
    IndexScanDesc indexScanDesc;
 
    /*
     * extract information from the node
     */
    indexRelationDesc = node->biss_RelationDesc;
    indexScanDesc = node->biss_ScanDesc;
 
    /*
     * When ending a parallel worker, copy the statistics gathered by the
     * worker back into shared memory so that it can be picked up by the main
     * process to report in EXPLAIN ANALYZE
     */
    if (node->biss_SharedInfo != NULL && IsParallelWorker())
    {
        IndexScanInstrumentation *winstrument;
 
        Assert(ParallelWorkerNumber <= node->biss_SharedInfo->num_workers);
        winstrument = &node->biss_SharedInfo->winstrument[ParallelWorkerNumber];
 
        /*
         * We have to accumulate the stats rather than performing a memcpy.
         * When a Gather/GatherMerge node finishes it will perform planner
         * shutdown on the workers.  On rescan it will spin up new workers
         * which will have a new BitmapIndexScanState and zeroed stats.
         */
        winstrument->nsearches += node->biss_Instrument.nsearches;
    }
 
    /*
     * close the index relation (no-op if we didn't open it)
     */
    if (indexScanDesc)
        index_endscan(indexScanDesc);
    if (indexRelationDesc)
        index_close(indexRelationDesc, NoLock);
}
 
/* ----------------------------------------------------------------
 *      ExecInitBitmapIndexScan
 *
 *      Initializes the index scan's state information.
 * ----------------------------------------------------------------
 */
BitmapIndexScanState *
ExecInitBitmapIndexScan(BitmapIndexScan *node, EState *estate, int eflags)
{
    BitmapIndexScanState *indexstate;
    LOCKMODE    lockmode;
 
    /* check for unsupported flags */
    Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
 
    /*
     * create state structure
     */
    indexstate = makeNode(BitmapIndexScanState);
    indexstate->ss.ps.plan = (Plan *) node;
    indexstate->ss.ps.state = estate;
    indexstate->ss.ps.ExecProcNode = ExecBitmapIndexScan;
 
    /* normally we don't make the result bitmap till runtime */
    indexstate->biss_result = NULL;
 
    /*
     * We do not open or lock the base relation here.  We assume that an
     * ancestor BitmapHeapScan node is holding AccessShareLock (or better) on
     * the heap relation throughout the execution of the plan tree.
     */
 
    indexstate->ss.ss_currentRelation = NULL;
    indexstate->ss.ss_currentScanDesc = NULL;
 
    /*
     * Miscellaneous initialization
     *
     * We do not need a standard exprcontext for this node, though we may
     * decide below to create a runtime-key exprcontext
     */
 
    /*
     * initialize child expressions
     *
     * We don't need to initialize targetlist or qual since neither are used.
     *
     * Note: we don't initialize all of the indexqual expression, only the
     * sub-parts corresponding to runtime keys (see below).
     */
 
    /*
     * If we are just doing EXPLAIN (ie, aren't going to run the plan), stop
     * here.  This allows an index-advisor plugin to EXPLAIN a plan containing
     * references to nonexistent indexes.
     */
    if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
        return indexstate;
 
    /* Open the index relation. */
    lockmode = exec_rt_fetch(node->scan.scanrelid, estate)->rellockmode;
    indexstate->biss_RelationDesc = index_open(node->indexid, lockmode);
 
    /*
     * Initialize index-specific scan state
     */
    indexstate->biss_RuntimeKeysReady = false;
    indexstate->biss_RuntimeKeys = NULL;
    indexstate->biss_NumRuntimeKeys = 0;
 
    /*
     * build the index scan keys from the index qualification
     */
    ExecIndexBuildScanKeys((PlanState *) indexstate,
                           indexstate->biss_RelationDesc,
                           node->indexqual,
                           false,
                           &indexstate->biss_ScanKeys,
                           &indexstate->biss_NumScanKeys,
                           &indexstate->biss_RuntimeKeys,
                           &indexstate->biss_NumRuntimeKeys,
                           &indexstate->biss_ArrayKeys,
                           &indexstate->biss_NumArrayKeys);
 
    /*
     * If we have runtime keys or array keys, we need an ExprContext to
     * evaluate them. We could just create a "standard" plan node exprcontext,
     * but to keep the code looking similar to nodeIndexscan.c, it seems
     * better to stick with the approach of using a separate ExprContext.
     */
    if (indexstate->biss_NumRuntimeKeys != 0 ||
        indexstate->biss_NumArrayKeys != 0)
    {
        ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;
 
        ExecAssignExprContext(estate, &indexstate->ss.ps);
        indexstate->biss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
        indexstate->ss.ps.ps_ExprContext = stdecontext;
    }
    else
    {
        indexstate->biss_RuntimeContext = NULL;
    }
 
    /*
     * Initialize scan descriptor.
     */
    indexstate->biss_ScanDesc =
        index_beginscan_bitmap(indexstate->biss_RelationDesc,
                               estate->es_snapshot,
                               &indexstate->biss_Instrument,
                               indexstate->biss_NumScanKeys);
 
    /*
     * If no run-time keys to calculate, go ahead and pass the scankeys to the
     * index AM.
     */
    if (indexstate->biss_NumRuntimeKeys == 0 &&
        indexstate->biss_NumArrayKeys == 0)
        index_rescan(indexstate->biss_ScanDesc,
                     indexstate->biss_ScanKeys, indexstate->biss_NumScanKeys,
                     NULL, 0);
 
    /*
     * all done.
     */
    return indexstate;
}
 
/* ----------------------------------------------------------------
 *      ExecBitmapIndexScanEstimate
 *
 *      Compute the amount of space we'll need in the parallel
 *      query DSM, and inform pcxt->estimator about our needs.
 * ----------------------------------------------------------------
 */
void
ExecBitmapIndexScanEstimate(BitmapIndexScanState *node, ParallelContext *pcxt)
{
    Size        size;
 
    /*
     * Parallel bitmap index scans are not supported, but we still need to
     * store the scan's instrumentation in DSM during parallel query
     */
    if (!node->ss.ps.instrument || pcxt->nworkers == 0)
        return;
 
    size = offsetof(SharedIndexScanInstrumentation, winstrument) +
        pcxt->nworkers * sizeof(IndexScanInstrumentation);
    shm_toc_estimate_chunk(&pcxt->estimator, size);
    shm_toc_estimate_keys(&pcxt->estimator, 1);
}
 
/* ----------------------------------------------------------------
 *      ExecBitmapIndexScanInitializeDSM
 *
 *      Set up bitmap index scan shared instrumentation.
 * ----------------------------------------------------------------
 */
void
ExecBitmapIndexScanInitializeDSM(BitmapIndexScanState *node,
                                 ParallelContext *pcxt)
{
    Size        size;
 
    /* don't need this if not instrumenting or no workers */
    if (!node->ss.ps.instrument || pcxt->nworkers == 0)
        return;
 
    size = offsetof(SharedIndexScanInstrumentation, winstrument) +
        pcxt->nworkers * sizeof(IndexScanInstrumentation);
    node->biss_SharedInfo =
        (SharedIndexScanInstrumentation *) shm_toc_allocate(pcxt->toc,
                                                            size);
    shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id,
                   node->biss_SharedInfo);
 
    /* Each per-worker area must start out as zeroes */
    memset(node->biss_SharedInfo, 0, size);
    node->biss_SharedInfo->num_workers = pcxt->nworkers;
}
 
/* ----------------------------------------------------------------
 *      ExecBitmapIndexScanInitializeWorker
 *
 *      Copy relevant information from TOC into planstate.
 * ----------------------------------------------------------------
 */
void
ExecBitmapIndexScanInitializeWorker(BitmapIndexScanState *node,
                                    ParallelWorkerContext *pwcxt)
{
    /* don't need this if not instrumenting */
    if (!node->ss.ps.instrument)
        return;
 
    node->biss_SharedInfo = (SharedIndexScanInstrumentation *)
        shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
}
 
/* ----------------------------------------------------------------
 * ExecBitmapIndexScanRetrieveInstrumentation
 *
 *      Transfer bitmap index scan statistics from DSM to private memory.
 * ----------------------------------------------------------------
 */
void
ExecBitmapIndexScanRetrieveInstrumentation(BitmapIndexScanState *node)
{
    SharedIndexScanInstrumentation *SharedInfo = node->biss_SharedInfo;
    size_t      size;
 
    if (SharedInfo == NULL)
        return;
 
    /* Create a copy of SharedInfo in backend-local memory */
    size = offsetof(SharedIndexScanInstrumentation, winstrument) +
        SharedInfo->num_workers * sizeof(IndexScanInstrumentation);
    node->biss_SharedInfo = palloc(size);
    memcpy(node->biss_SharedInfo, SharedInfo, size);
}