nodeIndexscan.c

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/*-------------------------------------------------------------------------
 *
 * nodeIndexscan.c
 *    Routines to support indexed scans of relations
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/executor/nodeIndexscan.c
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *      ExecIndexScan           scans a relation using an index
 *      IndexNext               retrieve next tuple using index
 *      IndexNextWithReorder    same, but recheck ORDER BY expressions
 *      ExecInitIndexScan       creates and initializes state info.
 *      ExecReScanIndexScan     rescans the indexed relation.
 *      ExecEndIndexScan        releases all storage.
 *      ExecIndexMarkPos        marks scan position.
 *      ExecIndexRestrPos       restores scan position.
 *      ExecIndexScanEstimate   estimates DSM space needed for parallel index scan
 *      ExecIndexScanInitializeDSM initialize DSM for parallel indexscan
 *      ExecIndexScanReInitializeDSM reinitialize DSM for fresh scan
 *      ExecIndexScanInitializeWorker attach to DSM info in parallel worker
 */
#include "postgres.h"
 
#include "access/nbtree.h"
#include "access/relscan.h"
#include "access/tableam.h"
#include "catalog/pg_am.h"
#include "executor/executor.h"
#include "executor/instrument.h"
#include "executor/nodeIndexscan.h"
#include "lib/pairingheap.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "utils/array.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/sortsupport.h"
 
/*
 * When an ordering operator is used, tuples fetched from the index that
 * need to be reordered are queued in a pairing heap, as ReorderTuples.
 */
typedef struct
{
    pairingheap_node ph_node;
    HeapTuple   htup;
    Datum      *orderbyvals;
    bool       *orderbynulls;
} ReorderTuple;
 
static TupleTableSlot *IndexNext(IndexScanState *node);
static TupleTableSlot *IndexNextWithReorder(IndexScanState *node);
static void EvalOrderByExpressions(IndexScanState *node, ExprContext *econtext);
static bool IndexRecheck(IndexScanState *node, TupleTableSlot *slot);
static int  cmp_orderbyvals(const Datum *adist, const bool *anulls,
                            const Datum *bdist, const bool *bnulls,
                            IndexScanState *node);
static int  reorderqueue_cmp(const pairingheap_node *a,
                             const pairingheap_node *b, void *arg);
static void reorderqueue_push(IndexScanState *node, TupleTableSlot *slot,
                              const Datum *orderbyvals, const bool *orderbynulls);
static HeapTuple reorderqueue_pop(IndexScanState *node);
 
 
/* ----------------------------------------------------------------
 *      IndexNext
 *
 *      Retrieve a tuple from the IndexScan node's currentRelation
 *      using the index specified in the IndexScanState information.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
IndexNext(IndexScanState *node)
{
    EState     *estate;
    ExprContext *econtext;
    ScanDirection direction;
    IndexScanDesc scandesc;
    TupleTableSlot *slot;
 
    /*
     * extract necessary information from index scan node
     */
    estate = node->ss.ps.state;
 
    /*
     * Determine which direction to scan the index in based on the plan's scan
     * direction and the current direction of execution.
     */
    direction = ScanDirectionCombine(estate->es_direction,
                                     ((IndexScan *) node->ss.ps.plan)->indexorderdir);
    scandesc = node->iss_ScanDesc;
    econtext = node->ss.ps.ps_ExprContext;
    slot = node->ss.ss_ScanTupleSlot;
 
    if (scandesc == NULL)
    {
        /*
         * We reach here if the index scan is not parallel, or if we're
         * serially executing an index scan that was planned to be parallel.
         */
        scandesc = index_beginscan(node->ss.ss_currentRelation,
                                   node->iss_RelationDesc,
                                   estate->es_snapshot,
                                   node->iss_Instrument,
                                   node->iss_NumScanKeys,
                                   node->iss_NumOrderByKeys,
                                   ScanRelIsReadOnly(&node->ss) ?
                                   SO_HINT_REL_READ_ONLY : SO_NONE);
 
        node->iss_ScanDesc = scandesc;
 
        /*
         * If no run-time keys to calculate or they are ready, go ahead and
         * pass the scankeys to the index AM.
         */
        if (node->iss_NumRuntimeKeys == 0 || node->iss_RuntimeKeysReady)
            index_rescan(scandesc,
                         node->iss_ScanKeys, node->iss_NumScanKeys,
                         node->iss_OrderByKeys, node->iss_NumOrderByKeys);
    }
 
    /*
     * ok, now that we have what we need, fetch the next tuple.
     */
    while (index_getnext_slot(scandesc, direction, slot))
    {
        CHECK_FOR_INTERRUPTS();
 
        /*
         * If the index was lossy, we have to recheck the index quals using
         * the fetched tuple.
         */
        if (scandesc->xs_recheck)
        {
            econtext->ecxt_scantuple = slot;
            if (!ExecQualAndReset(node->indexqualorig, econtext))
            {
                /* Fails recheck, so drop it and loop back for another */
                InstrCountFiltered2(node, 1);
                continue;
            }
        }
 
        return slot;
    }
 
    /*
     * if we get here it means the index scan failed so we are at the end of
     * the scan..
     */
    node->iss_ReachedEnd = true;
    return ExecClearTuple(slot);
}
 
/* ----------------------------------------------------------------
 *      IndexNextWithReorder
 *
 *      Like IndexNext, but this version can also re-check ORDER BY
 *      expressions, and reorder the tuples as necessary.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
IndexNextWithReorder(IndexScanState *node)
{
    EState     *estate;
    ExprContext *econtext;
    IndexScanDesc scandesc;
    TupleTableSlot *slot;
    ReorderTuple *topmost = NULL;
    bool        was_exact;
    Datum      *lastfetched_vals;
    bool       *lastfetched_nulls;
    int         cmp;
 
    estate = node->ss.ps.state;
 
    /*
     * Only forward scan is supported with reordering.  Note: we can get away
     * with just Asserting here because the system will not try to run the
     * plan backwards if ExecSupportsBackwardScan() says it won't work.
     * Currently, that is guaranteed because no index AMs support both
     * amcanorderbyop and amcanbackward; if any ever do,
     * ExecSupportsBackwardScan() will need to consider indexorderbys
     * explicitly.
     */
    Assert(!ScanDirectionIsBackward(((IndexScan *) node->ss.ps.plan)->indexorderdir));
    Assert(ScanDirectionIsForward(estate->es_direction));
 
    scandesc = node->iss_ScanDesc;
    econtext = node->ss.ps.ps_ExprContext;
    slot = node->ss.ss_ScanTupleSlot;
 
    if (scandesc == NULL)
    {
        /*
         * We reach here if the index scan is not parallel, or if we're
         * serially executing an index scan that was planned to be parallel.
         */
        scandesc = index_beginscan(node->ss.ss_currentRelation,
                                   node->iss_RelationDesc,
                                   estate->es_snapshot,
                                   node->iss_Instrument,
                                   node->iss_NumScanKeys,
                                   node->iss_NumOrderByKeys,
                                   ScanRelIsReadOnly(&node->ss) ?
                                   SO_HINT_REL_READ_ONLY : SO_NONE);
 
        node->iss_ScanDesc = scandesc;
 
        /*
         * If no run-time keys to calculate or they are ready, go ahead and
         * pass the scankeys to the index AM.
         */
        if (node->iss_NumRuntimeKeys == 0 || node->iss_RuntimeKeysReady)
            index_rescan(scandesc,
                         node->iss_ScanKeys, node->iss_NumScanKeys,
                         node->iss_OrderByKeys, node->iss_NumOrderByKeys);
    }
 
    for (;;)
    {
        CHECK_FOR_INTERRUPTS();
 
        /*
         * Check the reorder queue first.  If the topmost tuple in the queue
         * has an ORDER BY value smaller than (or equal to) the value last
         * returned by the index, we can return it now.
         */
        if (!pairingheap_is_empty(node->iss_ReorderQueue))
        {
            topmost = (ReorderTuple *) pairingheap_first(node->iss_ReorderQueue);
 
            if (node->iss_ReachedEnd ||
                cmp_orderbyvals(topmost->orderbyvals,
                                topmost->orderbynulls,
                                scandesc->xs_orderbyvals,
                                scandesc->xs_orderbynulls,
                                node) <= 0)
            {
                HeapTuple   tuple;
 
                tuple = reorderqueue_pop(node);
 
                /* Pass 'true', as the tuple in the queue is a palloc'd copy */
                ExecForceStoreHeapTuple(tuple, slot, true);
                return slot;
            }
        }
        else if (node->iss_ReachedEnd)
        {
            /* Queue is empty, and no more tuples from index.  We're done. */
            return ExecClearTuple(slot);
        }
 
        /*
         * Fetch next tuple from the index.
         */
next_indextuple:
        if (!index_getnext_slot(scandesc, ForwardScanDirection, slot))
        {
            /*
             * No more tuples from the index.  But we still need to drain any
             * remaining tuples from the queue before we're done.
             */
            node->iss_ReachedEnd = true;
            continue;
        }
 
        /*
         * If the index was lossy, we have to recheck the index quals and
         * ORDER BY expressions using the fetched tuple.
         */
        if (scandesc->xs_recheck)
        {
            econtext->ecxt_scantuple = slot;
            if (!ExecQualAndReset(node->indexqualorig, econtext))
            {
                /* Fails recheck, so drop it and loop back for another */
                InstrCountFiltered2(node, 1);
                /* allow this loop to be cancellable */
                CHECK_FOR_INTERRUPTS();
                goto next_indextuple;
            }
        }
 
        if (scandesc->xs_recheckorderby)
        {
            econtext->ecxt_scantuple = slot;
            ResetExprContext(econtext);
            EvalOrderByExpressions(node, econtext);
 
            /*
             * Was the ORDER BY value returned by the index accurate?  The
             * recheck flag means that the index can return inaccurate values,
             * but then again, the value returned for any particular tuple
             * could also be exactly correct.  Compare the value returned by
             * the index with the recalculated value.  (If the value returned
             * by the index happened to be exact right, we can often avoid
             * pushing the tuple to the queue, just to pop it back out again.)
             */
            cmp = cmp_orderbyvals(node->iss_OrderByValues,
                                  node->iss_OrderByNulls,
                                  scandesc->xs_orderbyvals,
                                  scandesc->xs_orderbynulls,
                                  node);
            if (cmp < 0)
                elog(ERROR, "index returned tuples in wrong order");
            else if (cmp == 0)
                was_exact = true;
            else
                was_exact = false;
            lastfetched_vals = node->iss_OrderByValues;
            lastfetched_nulls = node->iss_OrderByNulls;
        }
        else
        {
            was_exact = true;
            lastfetched_vals = scandesc->xs_orderbyvals;
            lastfetched_nulls = scandesc->xs_orderbynulls;
        }
 
        /*
         * Can we return this tuple immediately, or does it need to be pushed
         * to the reorder queue?  If the ORDER BY expression values returned
         * by the index were inaccurate, we can't return it yet, because the
         * next tuple from the index might need to come before this one. Also,
         * we can't return it yet if there are any smaller tuples in the queue
         * already.
         */
        if (!was_exact || (topmost && cmp_orderbyvals(lastfetched_vals,
                                                      lastfetched_nulls,
                                                      topmost->orderbyvals,
                                                      topmost->orderbynulls,
                                                      node) > 0))
        {
            /* Put this tuple to the queue */
            reorderqueue_push(node, slot, lastfetched_vals, lastfetched_nulls);
            continue;
        }
        else
        {
            /* Can return this tuple immediately. */
            return slot;
        }
    }
 
    /*
     * if we get here it means the index scan failed so we are at the end of
     * the scan..
     */
    return ExecClearTuple(slot);
}
 
/*
 * Calculate the expressions in the ORDER BY clause, based on the heap tuple.
 */
static void
EvalOrderByExpressions(IndexScanState *node, ExprContext *econtext)
{
    int         i;
    ListCell   *l;
    MemoryContext oldContext;
 
    oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 
    i = 0;
    foreach(l, node->indexorderbyorig)
    {
        ExprState  *orderby = (ExprState *) lfirst(l);
 
        node->iss_OrderByValues[i] = ExecEvalExpr(orderby,
                                                  econtext,
                                                  &node->iss_OrderByNulls[i]);
        i++;
    }
 
    MemoryContextSwitchTo(oldContext);
}
 
/*
 * IndexRecheck -- access method routine to recheck a tuple in EvalPlanQual
 */
static bool
IndexRecheck(IndexScanState *node, TupleTableSlot *slot)
{
    ExprContext *econtext;
 
    /*
     * extract necessary information from index scan node
     */
    econtext = node->ss.ps.ps_ExprContext;
 
    /* Does the tuple meet the indexqual condition? */
    econtext->ecxt_scantuple = slot;
    return ExecQualAndReset(node->indexqualorig, econtext);
}
 
 
/*
 * Compare ORDER BY expression values.
 */
static int
cmp_orderbyvals(const Datum *adist, const bool *anulls,
                const Datum *bdist, const bool *bnulls,
                IndexScanState *node)
{
    int         i;
    int         result;
 
    for (i = 0; i < node->iss_NumOrderByKeys; i++)
    {
        SortSupport ssup = &node->iss_SortSupport[i];
 
        /*
         * Handle nulls.  We only need to support NULLS LAST ordering, because
         * match_pathkeys_to_index() doesn't consider indexorderby
         * implementation otherwise.
         */
        if (anulls[i] && !bnulls[i])
            return 1;
        else if (!anulls[i] && bnulls[i])
            return -1;
        else if (anulls[i] && bnulls[i])
            return 0;
 
        result = ssup->comparator(adist[i], bdist[i], ssup);
        if (result != 0)
            return result;
    }
 
    return 0;
}
 
/*
 * Pairing heap provides getting topmost (greatest) element while KNN provides
 * ascending sort.  That's why we invert the sort order.
 */
static int
reorderqueue_cmp(const pairingheap_node *a, const pairingheap_node *b,
                 void *arg)
{
    const ReorderTuple *rta = (const ReorderTuple *) a;
    const ReorderTuple *rtb = (const ReorderTuple *) b;
    IndexScanState *node = (IndexScanState *) arg;
 
    /* exchange argument order to invert the sort order */
    return cmp_orderbyvals(rtb->orderbyvals, rtb->orderbynulls,
                           rta->orderbyvals, rta->orderbynulls,
                           node);
}
 
/*
 * Helper function to push a tuple to the reorder queue.
 */
static void
reorderqueue_push(IndexScanState *node, TupleTableSlot *slot,
                  const Datum *orderbyvals, const bool *orderbynulls)
{
    IndexScanDesc scandesc = node->iss_ScanDesc;
    EState     *estate = node->ss.ps.state;
    MemoryContext oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
    ReorderTuple *rt;
    int         i;
 
    rt = palloc_object(ReorderTuple);
    rt->htup = ExecCopySlotHeapTuple(slot);
    rt->orderbyvals = palloc_array(Datum, scandesc->numberOfOrderBys);
    rt->orderbynulls = palloc_array(bool, scandesc->numberOfOrderBys);
    for (i = 0; i < node->iss_NumOrderByKeys; i++)
    {
        if (!orderbynulls[i])
            rt->orderbyvals[i] = datumCopy(orderbyvals[i],
                                           node->iss_OrderByTypByVals[i],
                                           node->iss_OrderByTypLens[i]);
        else
            rt->orderbyvals[i] = (Datum) 0;
        rt->orderbynulls[i] = orderbynulls[i];
    }
    pairingheap_add(node->iss_ReorderQueue, &rt->ph_node);
 
    MemoryContextSwitchTo(oldContext);
}
 
/*
 * Helper function to pop the next tuple from the reorder queue.
 */
static HeapTuple
reorderqueue_pop(IndexScanState *node)
{
    HeapTuple   result;
    ReorderTuple *topmost;
    int         i;
 
    topmost = (ReorderTuple *) pairingheap_remove_first(node->iss_ReorderQueue);
 
    result = topmost->htup;
    for (i = 0; i < node->iss_NumOrderByKeys; i++)
    {
        if (!node->iss_OrderByTypByVals[i] && !topmost->orderbynulls[i])
            pfree(DatumGetPointer(topmost->orderbyvals[i]));
    }
    pfree(topmost->orderbyvals);
    pfree(topmost->orderbynulls);
    pfree(topmost);
 
    return result;
}
 
 
/* ----------------------------------------------------------------
 *      ExecIndexScan(node)
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecIndexScan(PlanState *pstate)
{
    IndexScanState *node = castNode(IndexScanState, pstate);
 
    /*
     * If we have runtime keys and they've not already been set up, do it now.
     */
    if (node->iss_NumRuntimeKeys != 0 && !node->iss_RuntimeKeysReady)
        ExecReScan((PlanState *) node);
 
    if (node->iss_NumOrderByKeys > 0)
        return ExecScan(&node->ss,
                        (ExecScanAccessMtd) IndexNextWithReorder,
                        (ExecScanRecheckMtd) IndexRecheck);
    else
        return ExecScan(&node->ss,
                        (ExecScanAccessMtd) IndexNext,
                        (ExecScanRecheckMtd) IndexRecheck);
}
 
/* ----------------------------------------------------------------
 *      ExecReScanIndexScan(node)
 *
 *      Recalculates the values of any scan keys whose value depends on
 *      information known at runtime, then rescans the indexed relation.
 *
 *      Updating the scan key was formerly done separately in
 *      ExecUpdateIndexScanKeys. Integrating it into ReScan makes
 *      rescans of indices and relations/general streams more uniform.
 * ----------------------------------------------------------------
 */
void
ExecReScanIndexScan(IndexScanState *node)
{
    /*
     * If we are doing runtime key calculations (ie, any of the index key
     * values weren't simple Consts), compute the new key values.  But first,
     * reset the 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 (node->iss_NumRuntimeKeys != 0)
    {
        ExprContext *econtext = node->iss_RuntimeContext;
 
        ResetExprContext(econtext);
        ExecIndexEvalRuntimeKeys(econtext,
                                 node->iss_RuntimeKeys,
                                 node->iss_NumRuntimeKeys);
    }
    node->iss_RuntimeKeysReady = true;
 
    /* flush the reorder queue */
    if (node->iss_ReorderQueue)
    {
        HeapTuple   tuple;
 
        while (!pairingheap_is_empty(node->iss_ReorderQueue))
        {
            tuple = reorderqueue_pop(node);
            heap_freetuple(tuple);
        }
    }
 
    /* reset index scan */
    if (node->iss_ScanDesc)
        index_rescan(node->iss_ScanDesc,
                     node->iss_ScanKeys, node->iss_NumScanKeys,
                     node->iss_OrderByKeys, node->iss_NumOrderByKeys);
    node->iss_ReachedEnd = false;
 
    ExecScanReScan(&node->ss);
}
 
 
/*
 * ExecIndexEvalRuntimeKeys
 *      Evaluate any runtime key values, and update the scankeys.
 */
void
ExecIndexEvalRuntimeKeys(ExprContext *econtext,
                         IndexRuntimeKeyInfo *runtimeKeys, int numRuntimeKeys)
{
    int         j;
    MemoryContext oldContext;
 
    /* We want to keep the key values in per-tuple memory */
    oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 
    for (j = 0; j < numRuntimeKeys; j++)
    {
        ScanKey     scan_key = runtimeKeys[j].scan_key;
        ExprState  *key_expr = runtimeKeys[j].key_expr;
        Datum       scanvalue;
        bool        isNull;
 
        /*
         * For each run-time key, extract the run-time expression and evaluate
         * it with respect to the current context.  We then stick the result
         * into the proper scan key.
         *
         * Note: the result of the eval could be a pass-by-ref value that's
         * stored in some outer scan's tuple, not in
         * econtext->ecxt_per_tuple_memory.  We assume that the outer tuple
         * will stay put throughout our scan.  If this is wrong, we could copy
         * the result into our context explicitly, but I think that's not
         * necessary.
         *
         * It's also entirely possible that the result of the eval is a
         * toasted value.  In this case we should forcibly detoast it, to
         * avoid repeat detoastings each time the value is examined by an
         * index support function.
         */
        scanvalue = ExecEvalExpr(key_expr,
                                 econtext,
                                 &isNull);
        if (isNull)
        {
            scan_key->sk_argument = scanvalue;
            scan_key->sk_flags |= SK_ISNULL;
        }
        else
        {
            if (runtimeKeys[j].key_toastable)
                scanvalue = PointerGetDatum(PG_DETOAST_DATUM(scanvalue));
            scan_key->sk_argument = scanvalue;
            scan_key->sk_flags &= ~SK_ISNULL;
        }
    }
 
    MemoryContextSwitchTo(oldContext);
}
 
/*
 * ExecIndexEvalArrayKeys
 *      Evaluate any array key values, and set up to iterate through arrays.
 *
 * Returns true if there are array elements to consider; false means there
 * is at least one null or empty array, so no match is possible.  On true
 * result, the scankeys are initialized with the first elements of the arrays.
 */
bool
ExecIndexEvalArrayKeys(ExprContext *econtext,
                       IndexArrayKeyInfo *arrayKeys, int numArrayKeys)
{
    bool        result = true;
    int         j;
    MemoryContext oldContext;
 
    /* We want to keep the arrays in per-tuple memory */
    oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 
    for (j = 0; j < numArrayKeys; j++)
    {
        ScanKey     scan_key = arrayKeys[j].scan_key;
        ExprState  *array_expr = arrayKeys[j].array_expr;
        Datum       arraydatum;
        bool        isNull;
        ArrayType  *arrayval;
        int16       elmlen;
        bool        elmbyval;
        char        elmalign;
        int         num_elems;
        Datum      *elem_values;
        bool       *elem_nulls;
 
        /*
         * Compute and deconstruct the array expression. (Notes in
         * ExecIndexEvalRuntimeKeys() apply here too.)
         */
        arraydatum = ExecEvalExpr(array_expr,
                                  econtext,
                                  &isNull);
        if (isNull)
        {
            result = false;
            break;              /* no point in evaluating more */
        }
        arrayval = DatumGetArrayTypeP(arraydatum);
        /* We could cache this data, but not clear it's worth it */
        get_typlenbyvalalign(ARR_ELEMTYPE(arrayval),
                             &elmlen, &elmbyval, &elmalign);
        deconstruct_array(arrayval,
                          ARR_ELEMTYPE(arrayval),
                          elmlen, elmbyval, elmalign,
                          &elem_values, &elem_nulls, &num_elems);
        if (num_elems <= 0)
        {
            result = false;
            break;              /* no point in evaluating more */
        }
 
        /*
         * Note: we expect the previous array data, if any, to be
         * automatically freed by resetting the per-tuple context; hence no
         * pfree's here.
         */
        arrayKeys[j].elem_values = elem_values;
        arrayKeys[j].elem_nulls = elem_nulls;
        arrayKeys[j].num_elems = num_elems;
        scan_key->sk_argument = elem_values[0];
        if (elem_nulls[0])
            scan_key->sk_flags |= SK_ISNULL;
        else
            scan_key->sk_flags &= ~SK_ISNULL;
        arrayKeys[j].next_elem = 1;
    }
 
    MemoryContextSwitchTo(oldContext);
 
    return result;
}
 
/*
 * ExecIndexAdvanceArrayKeys
 *      Advance to the next set of array key values, if any.
 *
 * Returns true if there is another set of values to consider, false if not.
 * On true result, the scankeys are initialized with the next set of values.
 */
bool
ExecIndexAdvanceArrayKeys(IndexArrayKeyInfo *arrayKeys, int numArrayKeys)
{
    bool        found = false;
    int         j;
 
    /*
     * Note we advance the rightmost array key most quickly, since it will
     * correspond to the lowest-order index column among the available
     * qualifications.  This is hypothesized to result in better locality of
     * access in the index.
     */
    for (j = numArrayKeys - 1; j >= 0; j--)
    {
        ScanKey     scan_key = arrayKeys[j].scan_key;
        int         next_elem = arrayKeys[j].next_elem;
        int         num_elems = arrayKeys[j].num_elems;
        Datum      *elem_values = arrayKeys[j].elem_values;
        bool       *elem_nulls = arrayKeys[j].elem_nulls;
 
        if (next_elem >= num_elems)
        {
            next_elem = 0;
            found = false;      /* need to advance next array key */
        }
        else
            found = true;
        scan_key->sk_argument = elem_values[next_elem];
        if (elem_nulls[next_elem])
            scan_key->sk_flags |= SK_ISNULL;
        else
            scan_key->sk_flags &= ~SK_ISNULL;
        arrayKeys[j].next_elem = next_elem + 1;
        if (found)
            break;
    }
 
    return found;
}
 
 
/* ----------------------------------------------------------------
 *      ExecEndIndexScan
 * ----------------------------------------------------------------
 */
void
ExecEndIndexScan(IndexScanState *node)
{
    Relation    indexRelationDesc;
    IndexScanDesc indexScanDesc;
 
    /*
     * extract information from the node
     */
    indexRelationDesc = node->iss_RelationDesc;
    indexScanDesc = node->iss_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->iss_SharedInfo != NULL && IsParallelWorker())
    {
        IndexScanInstrumentation *winstrument;
 
        Assert(ParallelWorkerNumber < node->iss_SharedInfo->num_workers);
        winstrument = &node->iss_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 IndexOnlyScanState and zeroed stats.
         */
        winstrument->nsearches += node->iss_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);
}
 
/* ----------------------------------------------------------------
 *      ExecIndexMarkPos
 *
 * Note: we assume that no caller attempts to set a mark before having read
 * at least one tuple.  Otherwise, iss_ScanDesc might still be NULL.
 * ----------------------------------------------------------------
 */
void
ExecIndexMarkPos(IndexScanState *node)
{
    EState     *estate = node->ss.ps.state;
    EPQState   *epqstate = estate->es_epq_active;
 
    if (epqstate != NULL)
    {
        /*
         * We are inside an EvalPlanQual recheck.  If a test tuple exists for
         * this relation, then we shouldn't access the index at all.  We would
         * instead need to save, and later restore, the state of the
         * relsubs_done flag, so that re-fetching the test tuple is possible.
         * However, given the assumption that no caller sets a mark at the
         * start of the scan, we can only get here with relsubs_done[i]
         * already set, and so no state need be saved.
         */
        Index       scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
 
        Assert(scanrelid > 0);
        if (epqstate->relsubs_slot[scanrelid - 1] != NULL ||
            epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
        {
            /* Verify the claim above */
            if (!epqstate->relsubs_done[scanrelid - 1])
                elog(ERROR, "unexpected ExecIndexMarkPos call in EPQ recheck");
            return;
        }
    }
 
    index_markpos(node->iss_ScanDesc);
}
 
/* ----------------------------------------------------------------
 *      ExecIndexRestrPos
 * ----------------------------------------------------------------
 */
void
ExecIndexRestrPos(IndexScanState *node)
{
    EState     *estate = node->ss.ps.state;
    EPQState   *epqstate = estate->es_epq_active;
 
    if (estate->es_epq_active != NULL)
    {
        /* See comments in ExecIndexMarkPos */
        Index       scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
 
        Assert(scanrelid > 0);
        if (epqstate->relsubs_slot[scanrelid - 1] != NULL ||
            epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
        {
            /* Verify the claim above */
            if (!epqstate->relsubs_done[scanrelid - 1])
                elog(ERROR, "unexpected ExecIndexRestrPos call in EPQ recheck");
            return;
        }
    }
 
    index_restrpos(node->iss_ScanDesc);
}
 
/* ----------------------------------------------------------------
 *      ExecInitIndexScan
 *
 *      Initializes the index scan's state information, creates
 *      scan keys, and opens the base and index relations.
 *
 *      Note: index scans have 2 sets of state information because
 *            we have to keep track of the base relation and the
 *            index relation.
 * ----------------------------------------------------------------
 */
IndexScanState *
ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
{
    IndexScanState *indexstate;
    Relation    currentRelation;
    LOCKMODE    lockmode;
 
    /*
     * create state structure
     */
    indexstate = makeNode(IndexScanState);
    indexstate->ss.ps.plan = (Plan *) node;
    indexstate->ss.ps.state = estate;
    indexstate->ss.ps.ExecProcNode = ExecIndexScan;
 
    /*
     * Miscellaneous initialization
     *
     * create expression context for node
     */
    ExecAssignExprContext(estate, &indexstate->ss.ps);
 
    /*
     * open the scan relation
     */
    currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
 
    indexstate->ss.ss_currentRelation = currentRelation;
    indexstate->ss.ss_currentScanDesc = NULL;   /* no heap scan here */
 
    /*
     * get the scan type from the relation descriptor.
     */
    ExecInitScanTupleSlot(estate, &indexstate->ss,
                          RelationGetDescr(currentRelation),
                          table_slot_callbacks(currentRelation),
                          TTS_FLAG_OBEYS_NOT_NULL_CONSTRAINTS);
 
    /*
     * Initialize result type and projection.
     */
    ExecInitResultTypeTL(&indexstate->ss.ps);
    ExecAssignScanProjectionInfo(&indexstate->ss);
 
    /*
     * initialize child expressions
     *
     * Note: we don't initialize all of the indexqual expression, only the
     * sub-parts corresponding to runtime keys (see below).  Likewise for
     * indexorderby, if any.  But the indexqualorig expression is always
     * initialized even though it will only be used in some uncommon cases ---
     * would be nice to improve that.  (Problem is that any SubPlans present
     * in the expression must be found now...)
     */
    indexstate->ss.ps.qual =
        ExecInitQual(node->scan.plan.qual, (PlanState *) indexstate);
    indexstate->indexqualorig =
        ExecInitQual(node->indexqualorig, (PlanState *) indexstate);
    indexstate->indexorderbyorig =
        ExecInitExprList(node->indexorderbyorig, (PlanState *) indexstate);
 
    /*
     * 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;
 
    /* Set up instrumentation of index scans if requested */
    if (estate->es_instrument)
        indexstate->iss_Instrument = palloc0_object(IndexScanInstrumentation);
 
    /* Open the index relation. */
    lockmode = exec_rt_fetch(node->scan.scanrelid, estate)->rellockmode;
    indexstate->iss_RelationDesc = index_open(node->indexid, lockmode);
 
    /*
     * Initialize index-specific scan state
     */
    indexstate->iss_RuntimeKeysReady = false;
    indexstate->iss_RuntimeKeys = NULL;
    indexstate->iss_NumRuntimeKeys = 0;
 
    /*
     * build the index scan keys from the index qualification
     */
    ExecIndexBuildScanKeys((PlanState *) indexstate,
                           indexstate->iss_RelationDesc,
                           node->indexqual,
                           false,
                           &indexstate->iss_ScanKeys,
                           &indexstate->iss_NumScanKeys,
                           &indexstate->iss_RuntimeKeys,
                           &indexstate->iss_NumRuntimeKeys,
                           NULL,    /* no ArrayKeys */
                           NULL);
 
    /*
     * any ORDER BY exprs have to be turned into scankeys in the same way
     */
    ExecIndexBuildScanKeys((PlanState *) indexstate,
                           indexstate->iss_RelationDesc,
                           node->indexorderby,
                           true,
                           &indexstate->iss_OrderByKeys,
                           &indexstate->iss_NumOrderByKeys,
                           &indexstate->iss_RuntimeKeys,
                           &indexstate->iss_NumRuntimeKeys,
                           NULL,    /* no ArrayKeys */
                           NULL);
 
    /* Initialize sort support, if we need to re-check ORDER BY exprs */
    if (indexstate->iss_NumOrderByKeys > 0)
    {
        int         numOrderByKeys = indexstate->iss_NumOrderByKeys;
        int         i;
        ListCell   *lco;
        ListCell   *lcx;
 
        /*
         * Prepare sort support, and look up the data type for each ORDER BY
         * expression.
         */
        Assert(numOrderByKeys == list_length(node->indexorderbyops));
        Assert(numOrderByKeys == list_length(node->indexorderbyorig));
        indexstate->iss_SortSupport = (SortSupportData *)
            palloc0(numOrderByKeys * sizeof(SortSupportData));
        indexstate->iss_OrderByTypByVals = (bool *)
            palloc(numOrderByKeys * sizeof(bool));
        indexstate->iss_OrderByTypLens = (int16 *)
            palloc(numOrderByKeys * sizeof(int16));
        i = 0;
        forboth(lco, node->indexorderbyops, lcx, node->indexorderbyorig)
        {
            Oid         orderbyop = lfirst_oid(lco);
            Node       *orderbyexpr = (Node *) lfirst(lcx);
            Oid         orderbyType = exprType(orderbyexpr);
            Oid         orderbyColl = exprCollation(orderbyexpr);
            SortSupport orderbysort = &indexstate->iss_SortSupport[i];
 
            /* Initialize sort support */
            orderbysort->ssup_cxt = CurrentMemoryContext;
            orderbysort->ssup_collation = orderbyColl;
            /* See cmp_orderbyvals() comments on NULLS LAST */
            orderbysort->ssup_nulls_first = false;
            /* ssup_attno is unused here and elsewhere */
            orderbysort->ssup_attno = 0;
            /* No abbreviation */
            orderbysort->abbreviate = false;
            PrepareSortSupportFromOrderingOp(orderbyop, orderbysort);
 
            get_typlenbyval(orderbyType,
                            &indexstate->iss_OrderByTypLens[i],
                            &indexstate->iss_OrderByTypByVals[i]);
            i++;
        }
 
        /* allocate arrays to hold the re-calculated distances */
        indexstate->iss_OrderByValues = (Datum *)
            palloc(numOrderByKeys * sizeof(Datum));
        indexstate->iss_OrderByNulls = (bool *)
            palloc(numOrderByKeys * sizeof(bool));
 
        /* and initialize the reorder queue */
        indexstate->iss_ReorderQueue = pairingheap_allocate(reorderqueue_cmp,
                                                            indexstate);
    }
 
    /*
     * If we have runtime keys, we need an ExprContext to evaluate them. The
     * node's standard context won't do because we want to reset that context
     * for every tuple.  So, build another context just like the other one...
     * -tgl 7/11/00
     */
    if (indexstate->iss_NumRuntimeKeys != 0)
    {
        ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;
 
        ExecAssignExprContext(estate, &indexstate->ss.ps);
        indexstate->iss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
        indexstate->ss.ps.ps_ExprContext = stdecontext;
    }
    else
    {
        indexstate->iss_RuntimeContext = NULL;
    }
 
    /*
     * all done.
     */
    return indexstate;
}
 
 
/*
 * ExecIndexBuildScanKeys
 *      Build the index scan keys from the index qualification expressions
 *
 * The index quals are passed to the index AM in the form of a ScanKey array.
 * This routine sets up the ScanKeys, fills in all constant fields of the
 * ScanKeys, and prepares information about the keys that have non-constant
 * comparison values.  We divide index qual expressions into five types:
 *
 * 1. Simple operator with constant comparison value ("indexkey op constant").
 * For these, we just fill in a ScanKey containing the constant value.
 *
 * 2. Simple operator with non-constant value ("indexkey op expression").
 * For these, we create a ScanKey with everything filled in except the
 * expression value, and set up an IndexRuntimeKeyInfo struct to drive
 * evaluation of the expression at the right times.
 *
 * 3. RowCompareExpr ("(indexkey, indexkey, ...) op (expr, expr, ...)").
 * For these, we create a header ScanKey plus a subsidiary ScanKey array,
 * as specified in access/skey.h.  The elements of the row comparison
 * can have either constant or non-constant comparison values.
 *
 * 4. ScalarArrayOpExpr ("indexkey op ANY (array-expression)").  If the index
 * supports amsearcharray, we handle these the same as simple operators,
 * setting the SK_SEARCHARRAY flag to tell the AM to handle them.  Otherwise,
 * we create a ScanKey with everything filled in except the comparison value,
 * and set up an IndexArrayKeyInfo struct to drive processing of the qual.
 * (Note that if we use an IndexArrayKeyInfo struct, the array expression is
 * always treated as requiring runtime evaluation, even if it's a constant.)
 *
 * 5. NullTest ("indexkey IS NULL/IS NOT NULL").  We just fill in the
 * ScanKey properly.
 *
 * This code is also used to prepare ORDER BY expressions for amcanorderbyop
 * indexes.  The behavior is exactly the same, except that we have to look up
 * the operator differently.  Note that only cases 1 and 2 are currently
 * possible for ORDER BY.
 *
 * Input params are:
 *
 * planstate: executor state node we are working for
 * index: the index we are building scan keys for
 * quals: indexquals (or indexorderbys) expressions
 * isorderby: true if processing ORDER BY exprs, false if processing quals
 * *runtimeKeys: ptr to pre-existing IndexRuntimeKeyInfos, or NULL if none
 * *numRuntimeKeys: number of pre-existing runtime keys
 *
 * Output params are:
 *
 * *scanKeys: receives ptr to array of ScanKeys
 * *numScanKeys: receives number of scankeys
 * *runtimeKeys: receives ptr to array of IndexRuntimeKeyInfos, or NULL if none
 * *numRuntimeKeys: receives number of runtime keys
 * *arrayKeys: receives ptr to array of IndexArrayKeyInfos, or NULL if none
 * *numArrayKeys: receives number of array keys
 *
 * Caller may pass NULL for arrayKeys and numArrayKeys to indicate that
 * IndexArrayKeyInfos are not supported.
 */
void
ExecIndexBuildScanKeys(PlanState *planstate, Relation index,
                       List *quals, bool isorderby,
                       ScanKey *scanKeys, int *numScanKeys,
                       IndexRuntimeKeyInfo **runtimeKeys, int *numRuntimeKeys,
                       IndexArrayKeyInfo **arrayKeys, int *numArrayKeys)
{
    ListCell   *qual_cell;
    ScanKey     scan_keys;
    IndexRuntimeKeyInfo *runtime_keys;
    IndexArrayKeyInfo *array_keys;
    int         n_scan_keys;
    int         n_runtime_keys;
    int         max_runtime_keys;
    int         n_array_keys;
    int         j;
 
    /* Allocate array for ScanKey structs: one per qual */
    n_scan_keys = list_length(quals);
    scan_keys = (ScanKey) palloc(n_scan_keys * sizeof(ScanKeyData));
 
    /*
     * runtime_keys array is dynamically resized as needed.  We handle it this
     * way so that the same runtime keys array can be shared between
     * indexquals and indexorderbys, which will be processed in separate calls
     * of this function.  Caller must be sure to pass in NULL/0 for first
     * call.
     */
    runtime_keys = *runtimeKeys;
    n_runtime_keys = max_runtime_keys = *numRuntimeKeys;
 
    /* Allocate array_keys as large as it could possibly need to be */
    array_keys = (IndexArrayKeyInfo *)
        palloc0(n_scan_keys * sizeof(IndexArrayKeyInfo));
    n_array_keys = 0;
 
    /*
     * for each opclause in the given qual, convert the opclause into a single
     * scan key
     */
    j = 0;
    foreach(qual_cell, quals)
    {
        Expr       *clause = (Expr *) lfirst(qual_cell);
        ScanKey     this_scan_key = &scan_keys[j++];
        Oid         opno;       /* operator's OID */
        RegProcedure opfuncid;  /* operator proc id used in scan */
        Oid         opfamily;   /* opfamily of index column */
        int         op_strategy;    /* operator's strategy number */
        Oid         op_lefttype;    /* operator's declared input types */
        Oid         op_righttype;
        Expr       *leftop;     /* expr on lhs of operator */
        Expr       *rightop;    /* expr on rhs ... */
        AttrNumber  varattno;   /* att number used in scan */
        int         indnkeyatts;
 
        indnkeyatts = IndexRelationGetNumberOfKeyAttributes(index);
        if (IsA(clause, OpExpr))
        {
            /* indexkey op const or indexkey op expression */
            int         flags = 0;
            Datum       scanvalue;
 
            opno = ((OpExpr *) clause)->opno;
            opfuncid = ((OpExpr *) clause)->opfuncid;
 
            /*
             * leftop should be the index key Var, possibly relabeled
             */
            leftop = (Expr *) get_leftop(clause);
 
            if (leftop && IsA(leftop, RelabelType))
                leftop = ((RelabelType *) leftop)->arg;
 
            Assert(leftop != NULL);
 
            if (!(IsA(leftop, Var) &&
                  ((Var *) leftop)->varno == INDEX_VAR))
                elog(ERROR, "indexqual doesn't have key on left side");
 
            varattno = ((Var *) leftop)->varattno;
            if (varattno < 1 || varattno > indnkeyatts)
                elog(ERROR, "bogus index qualification");
 
            /*
             * We have to look up the operator's strategy number.  This
             * provides a cross-check that the operator does match the index.
             */
            opfamily = index->rd_opfamily[varattno - 1];
 
            get_op_opfamily_properties(opno, opfamily, isorderby,
                                       &op_strategy,
                                       &op_lefttype,
                                       &op_righttype);
 
            if (isorderby)
                flags |= SK_ORDER_BY;
 
            /*
             * rightop is the constant or variable comparison value
             */
            rightop = (Expr *) get_rightop(clause);
 
            if (rightop && IsA(rightop, RelabelType))
                rightop = ((RelabelType *) rightop)->arg;
 
            Assert(rightop != NULL);
 
            if (IsA(rightop, Const))
            {
                /* OK, simple constant comparison value */
                scanvalue = ((Const *) rightop)->constvalue;
                if (((Const *) rightop)->constisnull)
                    flags |= SK_ISNULL;
            }
            else
            {
                /* Need to treat this one as a runtime key */
                if (n_runtime_keys >= max_runtime_keys)
                {
                    if (max_runtime_keys == 0)
                    {
                        max_runtime_keys = 8;
                        runtime_keys = (IndexRuntimeKeyInfo *)
                            palloc(max_runtime_keys * sizeof(IndexRuntimeKeyInfo));
                    }
                    else
                    {
                        max_runtime_keys *= 2;
                        runtime_keys = (IndexRuntimeKeyInfo *)
                            repalloc(runtime_keys, max_runtime_keys * sizeof(IndexRuntimeKeyInfo));
                    }
                }
                runtime_keys[n_runtime_keys].scan_key = this_scan_key;
                runtime_keys[n_runtime_keys].key_expr =
                    ExecInitExpr(rightop, planstate);
                runtime_keys[n_runtime_keys].key_toastable =
                    TypeIsToastable(op_righttype);
                n_runtime_keys++;
                scanvalue = (Datum) 0;
            }
 
            /*
             * initialize the scan key's fields appropriately
             */
            ScanKeyEntryInitialize(this_scan_key,
                                   flags,
                                   varattno,    /* attribute number to scan */
                                   op_strategy, /* op's strategy */
                                   op_righttype,    /* strategy subtype */
                                   ((OpExpr *) clause)->inputcollid,    /* collation */
                                   opfuncid,    /* reg proc to use */
                                   scanvalue);  /* constant */
        }
        else if (IsA(clause, RowCompareExpr))
        {
            /* (indexkey, indexkey, ...) op (expression, expression, ...) */
            RowCompareExpr *rc = (RowCompareExpr *) clause;
            ScanKey     first_sub_key;
            int         n_sub_key;
            ListCell   *largs_cell;
            ListCell   *rargs_cell;
            ListCell   *opnos_cell;
            ListCell   *collids_cell;
 
            Assert(!isorderby);
 
            first_sub_key = (ScanKey)
                palloc(list_length(rc->opnos) * sizeof(ScanKeyData));
            n_sub_key = 0;
 
            /* Scan RowCompare columns and generate subsidiary ScanKey items */
            forfour(largs_cell, rc->largs, rargs_cell, rc->rargs,
                    opnos_cell, rc->opnos, collids_cell, rc->inputcollids)
            {
                ScanKey     this_sub_key = &first_sub_key[n_sub_key];
                int         flags = SK_ROW_MEMBER;
                Datum       scanvalue;
                Oid         inputcollation;
 
                leftop = (Expr *) lfirst(largs_cell);
                rightop = (Expr *) lfirst(rargs_cell);
                opno = lfirst_oid(opnos_cell);
                inputcollation = lfirst_oid(collids_cell);
 
                /*
                 * leftop should be the index key Var, possibly relabeled
                 */
                if (leftop && IsA(leftop, RelabelType))
                    leftop = ((RelabelType *) leftop)->arg;
 
                Assert(leftop != NULL);
 
                if (!(IsA(leftop, Var) &&
                      ((Var *) leftop)->varno == INDEX_VAR))
                    elog(ERROR, "indexqual doesn't have key on left side");
 
                varattno = ((Var *) leftop)->varattno;
 
                /*
                 * We have to look up the operator's associated support
                 * function
                 */
                if (!index->rd_indam->amcanorder ||
                    varattno < 1 || varattno > indnkeyatts)
                    elog(ERROR, "bogus RowCompare index qualification");
                opfamily = index->rd_opfamily[varattno - 1];
 
                get_op_opfamily_properties(opno, opfamily, isorderby,
                                           &op_strategy,
                                           &op_lefttype,
                                           &op_righttype);
 
                if (op_strategy != rc->cmptype)
                    elog(ERROR, "RowCompare index qualification contains wrong operator");
 
                opfuncid = get_opfamily_proc(opfamily,
                                             op_lefttype,
                                             op_righttype,
                                             BTORDER_PROC);
                if (!RegProcedureIsValid(opfuncid))
                    elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
                         BTORDER_PROC, op_lefttype, op_righttype, opfamily);
 
                /*
                 * rightop is the constant or variable comparison value
                 */
                if (rightop && IsA(rightop, RelabelType))
                    rightop = ((RelabelType *) rightop)->arg;
 
                Assert(rightop != NULL);
 
                if (IsA(rightop, Const))
                {
                    /* OK, simple constant comparison value */
                    scanvalue = ((Const *) rightop)->constvalue;
                    if (((Const *) rightop)->constisnull)
                        flags |= SK_ISNULL;
                }
                else
                {
                    /* Need to treat this one as a runtime key */
                    if (n_runtime_keys >= max_runtime_keys)
                    {
                        if (max_runtime_keys == 0)
                        {
                            max_runtime_keys = 8;
                            runtime_keys = (IndexRuntimeKeyInfo *)
                                palloc(max_runtime_keys * sizeof(IndexRuntimeKeyInfo));
                        }
                        else
                        {
                            max_runtime_keys *= 2;
                            runtime_keys = (IndexRuntimeKeyInfo *)
                                repalloc(runtime_keys, max_runtime_keys * sizeof(IndexRuntimeKeyInfo));
                        }
                    }
                    runtime_keys[n_runtime_keys].scan_key = this_sub_key;
                    runtime_keys[n_runtime_keys].key_expr =
                        ExecInitExpr(rightop, planstate);
                    runtime_keys[n_runtime_keys].key_toastable =
                        TypeIsToastable(op_righttype);
                    n_runtime_keys++;
                    scanvalue = (Datum) 0;
                }
 
                /*
                 * initialize the subsidiary scan key's fields appropriately
                 */
                ScanKeyEntryInitialize(this_sub_key,
                                       flags,
                                       varattno,    /* attribute number */
                                       op_strategy, /* op's strategy */
                                       op_righttype,    /* strategy subtype */
                                       inputcollation,  /* collation */
                                       opfuncid,    /* reg proc to use */
                                       scanvalue);  /* constant */
                n_sub_key++;
            }
 
            /* Mark the last subsidiary scankey correctly */
            first_sub_key[n_sub_key - 1].sk_flags |= SK_ROW_END;
 
            /*
             * We don't use ScanKeyEntryInitialize for the header because it
             * isn't going to contain a valid sk_func pointer.
             */
            MemSet(this_scan_key, 0, sizeof(ScanKeyData));
            this_scan_key->sk_flags = SK_ROW_HEADER;
            this_scan_key->sk_attno = first_sub_key->sk_attno;
            this_scan_key->sk_strategy = rc->cmptype;
            /* sk_subtype, sk_collation, sk_func not used in a header */
            this_scan_key->sk_argument = PointerGetDatum(first_sub_key);
        }
        else if (IsA(clause, ScalarArrayOpExpr))
        {
            /* indexkey op ANY (array-expression) */
            ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) clause;
            int         flags = 0;
            Datum       scanvalue;
 
            Assert(!isorderby);
 
            Assert(saop->useOr);
            opno = saop->opno;
            opfuncid = saop->opfuncid;
 
            /*
             * leftop should be the index key Var, possibly relabeled
             */
            leftop = (Expr *) linitial(saop->args);
 
            if (leftop && IsA(leftop, RelabelType))
                leftop = ((RelabelType *) leftop)->arg;
 
            Assert(leftop != NULL);
 
            if (!(IsA(leftop, Var) &&
                  ((Var *) leftop)->varno == INDEX_VAR))
                elog(ERROR, "indexqual doesn't have key on left side");
 
            varattno = ((Var *) leftop)->varattno;
            if (varattno < 1 || varattno > indnkeyatts)
                elog(ERROR, "bogus index qualification");
 
            /*
             * We have to look up the operator's strategy number.  This
             * provides a cross-check that the operator does match the index.
             */
            opfamily = index->rd_opfamily[varattno - 1];
 
            get_op_opfamily_properties(opno, opfamily, isorderby,
                                       &op_strategy,
                                       &op_lefttype,
                                       &op_righttype);
 
            /*
             * rightop is the constant or variable array value
             */
            rightop = (Expr *) lsecond(saop->args);
 
            if (rightop && IsA(rightop, RelabelType))
                rightop = ((RelabelType *) rightop)->arg;
 
            Assert(rightop != NULL);
 
            if (index->rd_indam->amsearcharray)
            {
                /* Index AM will handle this like a simple operator */
                flags |= SK_SEARCHARRAY;
                if (IsA(rightop, Const))
                {
                    /* OK, simple constant comparison value */
                    scanvalue = ((Const *) rightop)->constvalue;
                    if (((Const *) rightop)->constisnull)
                        flags |= SK_ISNULL;
                }
                else
                {
                    /* Need to treat this one as a runtime key */
                    if (n_runtime_keys >= max_runtime_keys)
                    {
                        if (max_runtime_keys == 0)
                        {
                            max_runtime_keys = 8;
                            runtime_keys = (IndexRuntimeKeyInfo *)
                                palloc(max_runtime_keys * sizeof(IndexRuntimeKeyInfo));
                        }
                        else
                        {
                            max_runtime_keys *= 2;
                            runtime_keys = (IndexRuntimeKeyInfo *)
                                repalloc(runtime_keys, max_runtime_keys * sizeof(IndexRuntimeKeyInfo));
                        }
                    }
                    runtime_keys[n_runtime_keys].scan_key = this_scan_key;
                    runtime_keys[n_runtime_keys].key_expr =
                        ExecInitExpr(rightop, planstate);
 
                    /*
                     * Careful here: the runtime expression is not of
                     * op_righttype, but rather is an array of same; so
                     * TypeIsToastable() isn't helpful.  However, we can
                     * assume that all array types are toastable.
                     */
                    runtime_keys[n_runtime_keys].key_toastable = true;
                    n_runtime_keys++;
                    scanvalue = (Datum) 0;
                }
            }
            else
            {
                /* Executor has to expand the array value */
                array_keys[n_array_keys].scan_key = this_scan_key;
                array_keys[n_array_keys].array_expr =
                    ExecInitExpr(rightop, planstate);
                /* the remaining fields were zeroed by palloc0 */
                n_array_keys++;
                scanvalue = (Datum) 0;
            }
 
            /*
             * initialize the scan key's fields appropriately
             */
            ScanKeyEntryInitialize(this_scan_key,
                                   flags,
                                   varattno,    /* attribute number to scan */
                                   op_strategy, /* op's strategy */
                                   op_righttype,    /* strategy subtype */
                                   saop->inputcollid,   /* collation */
                                   opfuncid,    /* reg proc to use */
                                   scanvalue);  /* constant */
        }
        else if (IsA(clause, NullTest))
        {
            /* indexkey IS NULL or indexkey IS NOT NULL */
            NullTest   *ntest = (NullTest *) clause;
            int         flags;
 
            Assert(!isorderby);
 
            /*
             * argument should be the index key Var, possibly relabeled
             */
            leftop = ntest->arg;
 
            if (leftop && IsA(leftop, RelabelType))
                leftop = ((RelabelType *) leftop)->arg;
 
            Assert(leftop != NULL);
 
            if (!(IsA(leftop, Var) &&
                  ((Var *) leftop)->varno == INDEX_VAR))
                elog(ERROR, "NullTest indexqual has wrong key");
 
            varattno = ((Var *) leftop)->varattno;
 
            /*
             * initialize the scan key's fields appropriately
             */
            switch (ntest->nulltesttype)
            {
                case IS_NULL:
                    flags = SK_ISNULL | SK_SEARCHNULL;
                    break;
                case IS_NOT_NULL:
                    flags = SK_ISNULL | SK_SEARCHNOTNULL;
                    break;
                default:
                    elog(ERROR, "unrecognized nulltesttype: %d",
                         (int) ntest->nulltesttype);
                    flags = 0;  /* keep compiler quiet */
                    break;
            }
 
            ScanKeyEntryInitialize(this_scan_key,
                                   flags,
                                   varattno,    /* attribute number to scan */
                                   InvalidStrategy, /* no strategy */
                                   InvalidOid,  /* no strategy subtype */
                                   InvalidOid,  /* no collation */
                                   InvalidOid,  /* no reg proc for this */
                                   (Datum) 0);  /* constant */
        }
        else
            elog(ERROR, "unsupported indexqual type: %d",
                 (int) nodeTag(clause));
    }
 
    Assert(n_runtime_keys <= max_runtime_keys);
 
    /* Get rid of any unused arrays */
    if (n_array_keys == 0)
    {
        pfree(array_keys);
        array_keys = NULL;
    }
 
    /*
     * Return info to our caller.
     */
    *scanKeys = scan_keys;
    *numScanKeys = n_scan_keys;
    *runtimeKeys = runtime_keys;
    *numRuntimeKeys = n_runtime_keys;
    if (arrayKeys)
    {
        *arrayKeys = array_keys;
        *numArrayKeys = n_array_keys;
    }
    else if (n_array_keys != 0)
        elog(ERROR, "ScalarArrayOpExpr index qual found where not allowed");
}
 
/* ----------------------------------------------------------------
 *                      Parallel Scan Support
 * ----------------------------------------------------------------
 */
 
/* ----------------------------------------------------------------
 *      ExecIndexScanEstimate
 *
 *      Compute the amount of space we'll need in the parallel
 *      query DSM, and inform pcxt->estimator about our needs.
 * ----------------------------------------------------------------
 */
void
ExecIndexScanEstimate(IndexScanState *node,
                      ParallelContext *pcxt)
{
    EState     *estate = node->ss.ps.state;
 
    node->iss_PscanLen = index_parallelscan_estimate(node->iss_RelationDesc,
                                                     node->iss_NumScanKeys,
                                                     node->iss_NumOrderByKeys,
                                                     estate->es_snapshot);
    shm_toc_estimate_chunk(&pcxt->estimator, node->iss_PscanLen);
    shm_toc_estimate_keys(&pcxt->estimator, 1);
}
 
/* ----------------------------------------------------------------
 *      ExecIndexScanInitializeDSM
 *
 *      Set up a parallel index scan descriptor.
 * ----------------------------------------------------------------
 */
void
ExecIndexScanInitializeDSM(IndexScanState *node,
                           ParallelContext *pcxt)
{
    EState     *estate = node->ss.ps.state;
    ParallelIndexScanDesc piscan;
 
    piscan = shm_toc_allocate(pcxt->toc, node->iss_PscanLen);
    index_parallelscan_initialize(node->ss.ss_currentRelation,
                                  node->iss_RelationDesc,
                                  estate->es_snapshot,
                                  piscan);
    shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, piscan);
 
    node->iss_ScanDesc =
        index_beginscan_parallel(node->ss.ss_currentRelation,
                                 node->iss_RelationDesc,
                                 node->iss_Instrument,
                                 node->iss_NumScanKeys,
                                 node->iss_NumOrderByKeys,
                                 piscan,
                                 ScanRelIsReadOnly(&node->ss) ?
                                 SO_HINT_REL_READ_ONLY : SO_NONE);
 
    /*
     * If no run-time keys to calculate or they are ready, go ahead and pass
     * the scankeys to the index AM.
     */
    if (node->iss_NumRuntimeKeys == 0 || node->iss_RuntimeKeysReady)
        index_rescan(node->iss_ScanDesc,
                     node->iss_ScanKeys, node->iss_NumScanKeys,
                     node->iss_OrderByKeys, node->iss_NumOrderByKeys);
}
 
/* ----------------------------------------------------------------
 *      ExecIndexScanReInitializeDSM
 *
 *      Reset shared state before beginning a fresh scan.
 * ----------------------------------------------------------------
 */
void
ExecIndexScanReInitializeDSM(IndexScanState *node,
                             ParallelContext *pcxt)
{
    Assert(node->ss.ps.plan->parallel_aware);
    index_parallelrescan(node->iss_ScanDesc);
}
 
/* ----------------------------------------------------------------
 *      ExecIndexScanInitializeWorker
 *
 *      Copy relevant information from TOC into planstate.
 * ----------------------------------------------------------------
 */
void
ExecIndexScanInitializeWorker(IndexScanState *node,
                              ParallelWorkerContext *pwcxt)
{
    ParallelIndexScanDesc piscan;
 
    piscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
 
    node->iss_ScanDesc =
        index_beginscan_parallel(node->ss.ss_currentRelation,
                                 node->iss_RelationDesc,
                                 node->iss_Instrument,
                                 node->iss_NumScanKeys,
                                 node->iss_NumOrderByKeys,
                                 piscan,
                                 ScanRelIsReadOnly(&node->ss) ?
                                 SO_HINT_REL_READ_ONLY : SO_NONE);
 
    /*
     * If no run-time keys to calculate or they are ready, go ahead and pass
     * the scankeys to the index AM.
     */
    if (node->iss_NumRuntimeKeys == 0 || node->iss_RuntimeKeysReady)
        index_rescan(node->iss_ScanDesc,
                     node->iss_ScanKeys, node->iss_NumScanKeys,
                     node->iss_OrderByKeys, node->iss_NumOrderByKeys);
}
 
/*
 * Compute the amount of space we'll need for the shared instrumentation and
 * inform pcxt->estimator.
 */
void
ExecIndexScanInstrumentEstimate(IndexScanState *node,
                                ParallelContext *pcxt)
{
    Size        size;
 
    if (!node->ss.ps.instrument || pcxt->nworkers == 0)
        return;
 
    /*
     * This size calculation is trivial enough that we don't bother saving it
     * in the IndexScanState. We'll recalculate the needed size in
     * ExecIndexScanInstrumentInitDSM().
     */
    size = add_size(offsetof(SharedIndexScanInstrumentation, winstrument),
                    mul_size(pcxt->nworkers, sizeof(IndexScanInstrumentation)));
    shm_toc_estimate_chunk(&pcxt->estimator, size);
    shm_toc_estimate_keys(&pcxt->estimator, 1);
}
 
/*
 * Set up parallel index scan instrumentation.
 */
void
ExecIndexScanInstrumentInitDSM(IndexScanState *node,
                               ParallelContext *pcxt)
{
    Size        size;
 
    if (!node->ss.ps.instrument || pcxt->nworkers == 0)
        return;
 
    size = add_size(offsetof(SharedIndexScanInstrumentation, winstrument),
                    mul_size(pcxt->nworkers, sizeof(IndexScanInstrumentation)));
    node->iss_SharedInfo =
        (SharedIndexScanInstrumentation *) shm_toc_allocate(pcxt->toc, size);
 
    /* Each per-worker area must start out as zeroes */
    memset(node->iss_SharedInfo, 0, size);
    node->iss_SharedInfo->num_workers = pcxt->nworkers;
    shm_toc_insert(pcxt->toc,
                   node->ss.ps.plan->plan_node_id +
                   PARALLEL_KEY_SCAN_INSTRUMENT_OFFSET,
                   node->iss_SharedInfo);
}
 
/*
 * Look up and save the location of the shared instrumentation.
 */
void
ExecIndexScanInstrumentInitWorker(IndexScanState *node,
                                  ParallelWorkerContext *pwcxt)
{
    if (!node->ss.ps.instrument)
        return;
 
    node->iss_SharedInfo = (SharedIndexScanInstrumentation *)
        shm_toc_lookup(pwcxt->toc,
                       node->ss.ps.plan->plan_node_id +
                       PARALLEL_KEY_SCAN_INSTRUMENT_OFFSET,
                       false);
}
 
/* ----------------------------------------------------------------
 * ExecIndexScanRetrieveInstrumentation
 *
 *      Transfer index scan statistics from DSM to private memory.
 * ----------------------------------------------------------------
 */
void
ExecIndexScanRetrieveInstrumentation(IndexScanState *node)
{
    SharedIndexScanInstrumentation *SharedInfo = node->iss_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->iss_SharedInfo = palloc(size);
    memcpy(node->iss_SharedInfo, SharedInfo, size);
}