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Functions

nodeHashjoin.h File Reference

#include "nodes/execnodes.h"
#include "storage/buffile.h"
Include dependency graph for nodeHashjoin.h:
This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Functions

HashJoinStateExecInitHashJoin (HashJoin *node, EState *estate, int eflags)
TupleTableSlotExecHashJoin (HashJoinState *node)
void ExecEndHashJoin (HashJoinState *node)
void ExecReScanHashJoin (HashJoinState *node)
void ExecHashJoinSaveTuple (MinimalTuple tuple, uint32 hashvalue, BufFile **fileptr)

Function Documentation

void ExecEndHashJoin ( HashJoinState node  ) 
TupleTableSlot* ExecHashJoin ( HashJoinState node  ) 

Definition at line 62 of file nodeHashjoin.c.

References Assert, CHECK_FOR_INTERRUPTS, HashJoinTableData::curbatch, ExprContext::ecxt_innertuple, ExprContext::ecxt_outertuple, elog, ERROR, ExecFetchSlotMinimalTuple(), ExecHashGetBucketAndBatch(), ExecHashGetSkewBucket(), ExecHashJoinNewBatch(), ExecHashJoinOuterGetTuple(), ExecHashJoinSaveTuple(), ExecHashTableCreate(), ExecPrepHashTableForUnmatched(), ExecProcNode(), ExecProject(), ExecQual(), ExecScanHashBucket(), ExecScanHashTableForUnmatched(), ExprEndResult, ExprMultipleResult, HashState::hashtable, HeapTupleHeaderSetMatch, HJ_BUILD_HASHTABLE, HashJoinState::hj_CurBucketNo, HashJoinState::hj_CurHashValue, HashJoinState::hj_CurSkewBucketNo, HashJoinState::hj_CurTuple, HJ_FILL_INNER, HJ_FILL_INNER_TUPLES, HJ_FILL_OUTER, HJ_FILL_OUTER_TUPLE, HashJoinState::hj_FirstOuterTupleSlot, HashJoinState::hj_HashOperators, HashJoinState::hj_HashTable, HashJoinState::hj_JoinState, HashJoinState::hj_MatchedOuter, HJ_NEED_NEW_BATCH, HJ_NEED_NEW_OUTER, HashJoinState::hj_NullInnerTupleSlot, HashJoinState::hj_NullOuterTupleSlot, HashJoinState::hj_OuterNotEmpty, HJ_SCAN_BUCKET, HJTUPLE_MINTUPLE, innerPlanState, InstrCountFiltered1, InstrCountFiltered2, INVALID_SKEW_BUCKET_NO, JOIN_ANTI, JOIN_SEMI, JoinState::joinqual, JoinState::jointype, HashJoinState::js, MultiExecProcNode(), HashJoinTableData::nbatch, HashJoinTableData::nbatch_outstart, NIL, NULL, HashJoinTableData::outerBatchFile, outerPlanState, PlanState::plan, HashState::ps, JoinState::ps, PlanState::ps_ExprContext, PlanState::ps_ProjInfo, PlanState::ps_TupFromTlist, PlanState::qual, ResetExprContext, Plan::startup_cost, Plan::total_cost, HashJoinTableData::totalTuples, and TupIsNull.

Referenced by ExecProcNode().

{
    PlanState  *outerNode;
    HashState  *hashNode;
    List       *joinqual;
    List       *otherqual;
    ExprContext *econtext;
    ExprDoneCond isDone;
    HashJoinTable hashtable;
    TupleTableSlot *outerTupleSlot;
    uint32      hashvalue;
    int         batchno;

    /*
     * get information from HashJoin node
     */
    joinqual = node->js.joinqual;
    otherqual = node->js.ps.qual;
    hashNode = (HashState *) innerPlanState(node);
    outerNode = outerPlanState(node);
    hashtable = node->hj_HashTable;
    econtext = node->js.ps.ps_ExprContext;

    /*
     * Check to see if we're still projecting out tuples from a previous join
     * tuple (because there is a function-returning-set in the projection
     * expressions).  If so, try to project another one.
     */
    if (node->js.ps.ps_TupFromTlist)
    {
        TupleTableSlot *result;

        result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
        if (isDone == ExprMultipleResult)
            return result;
        /* Done with that source tuple... */
        node->js.ps.ps_TupFromTlist = false;
    }

    /*
     * Reset per-tuple memory context to free any expression evaluation
     * storage allocated in the previous tuple cycle.  Note this can't happen
     * until we're done projecting out tuples from a join tuple.
     */
    ResetExprContext(econtext);

    /*
     * run the hash join state machine
     */
    for (;;)
    {
        switch (node->hj_JoinState)
        {
            case HJ_BUILD_HASHTABLE:

                /*
                 * First time through: build hash table for inner relation.
                 */
                Assert(hashtable == NULL);

                /*
                 * If the outer relation is completely empty, and it's not
                 * right/full join, we can quit without building the hash
                 * table.  However, for an inner join it is only a win to
                 * check this when the outer relation's startup cost is less
                 * than the projected cost of building the hash table.
                 * Otherwise it's best to build the hash table first and see
                 * if the inner relation is empty.  (When it's a left join, we
                 * should always make this check, since we aren't going to be
                 * able to skip the join on the strength of an empty inner
                 * relation anyway.)
                 *
                 * If we are rescanning the join, we make use of information
                 * gained on the previous scan: don't bother to try the
                 * prefetch if the previous scan found the outer relation
                 * nonempty. This is not 100% reliable since with new
                 * parameters the outer relation might yield different
                 * results, but it's a good heuristic.
                 *
                 * The only way to make the check is to try to fetch a tuple
                 * from the outer plan node.  If we succeed, we have to stash
                 * it away for later consumption by ExecHashJoinOuterGetTuple.
                 */
                if (HJ_FILL_INNER(node))
                {
                    /* no chance to not build the hash table */
                    node->hj_FirstOuterTupleSlot = NULL;
                }
                else if (HJ_FILL_OUTER(node) ||
                         (outerNode->plan->startup_cost < hashNode->ps.plan->total_cost &&
                          !node->hj_OuterNotEmpty))
                {
                    node->hj_FirstOuterTupleSlot = ExecProcNode(outerNode);
                    if (TupIsNull(node->hj_FirstOuterTupleSlot))
                    {
                        node->hj_OuterNotEmpty = false;
                        return NULL;
                    }
                    else
                        node->hj_OuterNotEmpty = true;
                }
                else
                    node->hj_FirstOuterTupleSlot = NULL;

                /*
                 * create the hash table
                 */
                hashtable = ExecHashTableCreate((Hash *) hashNode->ps.plan,
                                                node->hj_HashOperators,
                                                HJ_FILL_INNER(node));
                node->hj_HashTable = hashtable;

                /*
                 * execute the Hash node, to build the hash table
                 */
                hashNode->hashtable = hashtable;
                (void) MultiExecProcNode((PlanState *) hashNode);

                /*
                 * If the inner relation is completely empty, and we're not
                 * doing a left outer join, we can quit without scanning the
                 * outer relation.
                 */
                if (hashtable->totalTuples == 0 && !HJ_FILL_OUTER(node))
                    return NULL;

                /*
                 * need to remember whether nbatch has increased since we
                 * began scanning the outer relation
                 */
                hashtable->nbatch_outstart = hashtable->nbatch;

                /*
                 * Reset OuterNotEmpty for scan.  (It's OK if we fetched a
                 * tuple above, because ExecHashJoinOuterGetTuple will
                 * immediately set it again.)
                 */
                node->hj_OuterNotEmpty = false;

                node->hj_JoinState = HJ_NEED_NEW_OUTER;

                /* FALL THRU */

            case HJ_NEED_NEW_OUTER:

                /*
                 * We don't have an outer tuple, try to get the next one
                 */
                outerTupleSlot = ExecHashJoinOuterGetTuple(outerNode,
                                                           node,
                                                           &hashvalue);
                if (TupIsNull(outerTupleSlot))
                {
                    /* end of batch, or maybe whole join */
                    if (HJ_FILL_INNER(node))
                    {
                        /* set up to scan for unmatched inner tuples */
                        ExecPrepHashTableForUnmatched(node);
                        node->hj_JoinState = HJ_FILL_INNER_TUPLES;
                    }
                    else
                        node->hj_JoinState = HJ_NEED_NEW_BATCH;
                    continue;
                }

                econtext->ecxt_outertuple = outerTupleSlot;
                node->hj_MatchedOuter = false;

                /*
                 * Find the corresponding bucket for this tuple in the main
                 * hash table or skew hash table.
                 */
                node->hj_CurHashValue = hashvalue;
                ExecHashGetBucketAndBatch(hashtable, hashvalue,
                                          &node->hj_CurBucketNo, &batchno);
                node->hj_CurSkewBucketNo = ExecHashGetSkewBucket(hashtable,
                                                                 hashvalue);
                node->hj_CurTuple = NULL;

                /*
                 * The tuple might not belong to the current batch (where
                 * "current batch" includes the skew buckets if any).
                 */
                if (batchno != hashtable->curbatch &&
                    node->hj_CurSkewBucketNo == INVALID_SKEW_BUCKET_NO)
                {
                    /*
                     * Need to postpone this outer tuple to a later batch.
                     * Save it in the corresponding outer-batch file.
                     */
                    Assert(batchno > hashtable->curbatch);
                    ExecHashJoinSaveTuple(ExecFetchSlotMinimalTuple(outerTupleSlot),
                                          hashvalue,
                                        &hashtable->outerBatchFile[batchno]);
                    /* Loop around, staying in HJ_NEED_NEW_OUTER state */
                    continue;
                }

                /* OK, let's scan the bucket for matches */
                node->hj_JoinState = HJ_SCAN_BUCKET;

                /* FALL THRU */

            case HJ_SCAN_BUCKET:

                /*
                 * We check for interrupts here because this corresponds to
                 * where we'd fetch a row from a child plan node in other join
                 * types.
                 */
                CHECK_FOR_INTERRUPTS();

                /*
                 * Scan the selected hash bucket for matches to current outer
                 */
                if (!ExecScanHashBucket(node, econtext))
                {
                    /* out of matches; check for possible outer-join fill */
                    node->hj_JoinState = HJ_FILL_OUTER_TUPLE;
                    continue;
                }

                /*
                 * We've got a match, but still need to test non-hashed quals.
                 * ExecScanHashBucket already set up all the state needed to
                 * call ExecQual.
                 *
                 * If we pass the qual, then save state for next call and have
                 * ExecProject form the projection, store it in the tuple
                 * table, and return the slot.
                 *
                 * Only the joinquals determine tuple match status, but all
                 * quals must pass to actually return the tuple.
                 */
                if (joinqual == NIL || ExecQual(joinqual, econtext, false))
                {
                    node->hj_MatchedOuter = true;
                    HeapTupleHeaderSetMatch(HJTUPLE_MINTUPLE(node->hj_CurTuple));

                    /* In an antijoin, we never return a matched tuple */
                    if (node->js.jointype == JOIN_ANTI)
                    {
                        node->hj_JoinState = HJ_NEED_NEW_OUTER;
                        continue;
                    }

                    /*
                     * In a semijoin, we'll consider returning the first
                     * match, but after that we're done with this outer tuple.
                     */
                    if (node->js.jointype == JOIN_SEMI)
                        node->hj_JoinState = HJ_NEED_NEW_OUTER;

                    if (otherqual == NIL ||
                        ExecQual(otherqual, econtext, false))
                    {
                        TupleTableSlot *result;

                        result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);

                        if (isDone != ExprEndResult)
                        {
                            node->js.ps.ps_TupFromTlist =
                                (isDone == ExprMultipleResult);
                            return result;
                        }
                    }
                    else
                        InstrCountFiltered2(node, 1);
                }
                else
                    InstrCountFiltered1(node, 1);
                break;

            case HJ_FILL_OUTER_TUPLE:

                /*
                 * The current outer tuple has run out of matches, so check
                 * whether to emit a dummy outer-join tuple.  Whether we emit
                 * one or not, the next state is NEED_NEW_OUTER.
                 */
                node->hj_JoinState = HJ_NEED_NEW_OUTER;

                if (!node->hj_MatchedOuter &&
                    HJ_FILL_OUTER(node))
                {
                    /*
                     * Generate a fake join tuple with nulls for the inner
                     * tuple, and return it if it passes the non-join quals.
                     */
                    econtext->ecxt_innertuple = node->hj_NullInnerTupleSlot;

                    if (otherqual == NIL ||
                        ExecQual(otherqual, econtext, false))
                    {
                        TupleTableSlot *result;

                        result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);

                        if (isDone != ExprEndResult)
                        {
                            node->js.ps.ps_TupFromTlist =
                                (isDone == ExprMultipleResult);
                            return result;
                        }
                    }
                    else
                        InstrCountFiltered2(node, 1);
                }
                break;

            case HJ_FILL_INNER_TUPLES:

                /*
                 * We have finished a batch, but we are doing right/full join,
                 * so any unmatched inner tuples in the hashtable have to be
                 * emitted before we continue to the next batch.
                 */
                if (!ExecScanHashTableForUnmatched(node, econtext))
                {
                    /* no more unmatched tuples */
                    node->hj_JoinState = HJ_NEED_NEW_BATCH;
                    continue;
                }

                /*
                 * Generate a fake join tuple with nulls for the outer tuple,
                 * and return it if it passes the non-join quals.
                 */
                econtext->ecxt_outertuple = node->hj_NullOuterTupleSlot;

                if (otherqual == NIL ||
                    ExecQual(otherqual, econtext, false))
                {
                    TupleTableSlot *result;

                    result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);

                    if (isDone != ExprEndResult)
                    {
                        node->js.ps.ps_TupFromTlist =
                            (isDone == ExprMultipleResult);
                        return result;
                    }
                }
                else
                    InstrCountFiltered2(node, 1);
                break;

            case HJ_NEED_NEW_BATCH:

                /*
                 * Try to advance to next batch.  Done if there are no more.
                 */
                if (!ExecHashJoinNewBatch(node))
                    return NULL;    /* end of join */
                node->hj_JoinState = HJ_NEED_NEW_OUTER;
                break;

            default:
                elog(ERROR, "unrecognized hashjoin state: %d",
                     (int) node->hj_JoinState);
        }
    }
}

void ExecHashJoinSaveTuple ( MinimalTuple  tuple,
uint32  hashvalue,
BufFile **  fileptr 
)

Definition at line 871 of file nodeHashjoin.c.

References BufFileCreateTemp(), BufFileWrite(), ereport, errcode_for_file_access(), errmsg(), ERROR, NULL, and MinimalTupleData::t_len.

Referenced by ExecHashIncreaseNumBatches(), ExecHashJoin(), ExecHashRemoveNextSkewBucket(), and ExecHashTableInsert().

{
    BufFile    *file = *fileptr;
    size_t      written;

    if (file == NULL)
    {
        /* First write to this batch file, so open it. */
        file = BufFileCreateTemp(false);
        *fileptr = file;
    }

    written = BufFileWrite(file, (void *) &hashvalue, sizeof(uint32));
    if (written != sizeof(uint32))
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not write to hash-join temporary file: %m")));

    written = BufFileWrite(file, (void *) tuple, tuple->t_len);
    if (written != tuple->t_len)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not write to hash-join temporary file: %m")));
}

HashJoinState* ExecInitHashJoin ( HashJoin node,
EState estate,
int  eflags 
)

Definition at line 435 of file nodeHashjoin.c.

References FuncExprState::args, Assert, elog, ERROR, EXEC_FLAG_BACKWARD, EXEC_FLAG_MARK, ExecAssignExprContext(), ExecAssignProjectionInfo(), ExecAssignResultTypeFromTL(), ExecGetResultType(), ExecInitExpr(), ExecInitExtraTupleSlot(), ExecInitNode(), ExecInitNullTupleSlot(), ExecInitResultTupleSlot(), ExecSetSlotDescriptor(), ExprState::expr, HashJoin::hashclauses, HashJoinState::hashclauses, HashJoinState::hj_CurBucketNo, HashJoinState::hj_CurHashValue, HashJoinState::hj_CurSkewBucketNo, HashJoinState::hj_CurTuple, HashJoinState::hj_FirstOuterTupleSlot, HashJoinState::hj_HashOperators, HashJoinState::hj_HashTable, HashJoinState::hj_HashTupleSlot, HashJoinState::hj_InnerHashKeys, HashJoinState::hj_JoinState, HashJoinState::hj_MatchedOuter, HashJoinState::hj_NullInnerTupleSlot, HashJoinState::hj_NullOuterTupleSlot, HashJoinState::hj_OuterHashKeys, HashJoinState::hj_OuterNotEmpty, HashJoinState::hj_OuterTupleSlot, innerPlan, innerPlanState, IsA, HashJoin::join, JOIN_ANTI, JOIN_FULL, JOIN_INNER, JOIN_LEFT, JOIN_RIGHT, JOIN_SEMI, Join::joinqual, JoinState::joinqual, Join::jointype, JoinState::jointype, HashJoinState::js, lappend(), lappend_oid(), lfirst, linitial, lsecond, makeNode, NULL, OpExpr::opno, outerPlan, outerPlanState, Join::plan, PlanState::plan, HashState::ps, JoinState::ps, PlanState::ps_ResultTupleSlot, PlanState::ps_TupFromTlist, Plan::qual, PlanState::qual, PlanState::state, Plan::targetlist, PlanState::targetlist, and FuncExprState::xprstate.

Referenced by ExecInitNode().

{
    HashJoinState *hjstate;
    Plan       *outerNode;
    Hash       *hashNode;
    List       *lclauses;
    List       *rclauses;
    List       *hoperators;
    ListCell   *l;

    /* check for unsupported flags */
    Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

    /*
     * create state structure
     */
    hjstate = makeNode(HashJoinState);
    hjstate->js.ps.plan = (Plan *) node;
    hjstate->js.ps.state = estate;

    /*
     * Miscellaneous initialization
     *
     * create expression context for node
     */
    ExecAssignExprContext(estate, &hjstate->js.ps);

    /*
     * initialize child expressions
     */
    hjstate->js.ps.targetlist = (List *)
        ExecInitExpr((Expr *) node->join.plan.targetlist,
                     (PlanState *) hjstate);
    hjstate->js.ps.qual = (List *)
        ExecInitExpr((Expr *) node->join.plan.qual,
                     (PlanState *) hjstate);
    hjstate->js.jointype = node->join.jointype;
    hjstate->js.joinqual = (List *)
        ExecInitExpr((Expr *) node->join.joinqual,
                     (PlanState *) hjstate);
    hjstate->hashclauses = (List *)
        ExecInitExpr((Expr *) node->hashclauses,
                     (PlanState *) hjstate);

    /*
     * initialize child nodes
     *
     * Note: we could suppress the REWIND flag for the inner input, which
     * would amount to betting that the hash will be a single batch.  Not
     * clear if this would be a win or not.
     */
    outerNode = outerPlan(node);
    hashNode = (Hash *) innerPlan(node);

    outerPlanState(hjstate) = ExecInitNode(outerNode, estate, eflags);
    innerPlanState(hjstate) = ExecInitNode((Plan *) hashNode, estate, eflags);

    /*
     * tuple table initialization
     */
    ExecInitResultTupleSlot(estate, &hjstate->js.ps);
    hjstate->hj_OuterTupleSlot = ExecInitExtraTupleSlot(estate);

    /* set up null tuples for outer joins, if needed */
    switch (node->join.jointype)
    {
        case JOIN_INNER:
        case JOIN_SEMI:
            break;
        case JOIN_LEFT:
        case JOIN_ANTI:
            hjstate->hj_NullInnerTupleSlot =
                ExecInitNullTupleSlot(estate,
                                 ExecGetResultType(innerPlanState(hjstate)));
            break;
        case JOIN_RIGHT:
            hjstate->hj_NullOuterTupleSlot =
                ExecInitNullTupleSlot(estate,
                                 ExecGetResultType(outerPlanState(hjstate)));
            break;
        case JOIN_FULL:
            hjstate->hj_NullOuterTupleSlot =
                ExecInitNullTupleSlot(estate,
                                 ExecGetResultType(outerPlanState(hjstate)));
            hjstate->hj_NullInnerTupleSlot =
                ExecInitNullTupleSlot(estate,
                                 ExecGetResultType(innerPlanState(hjstate)));
            break;
        default:
            elog(ERROR, "unrecognized join type: %d",
                 (int) node->join.jointype);
    }

    /*
     * now for some voodoo.  our temporary tuple slot is actually the result
     * tuple slot of the Hash node (which is our inner plan).  we can do this
     * because Hash nodes don't return tuples via ExecProcNode() -- instead
     * the hash join node uses ExecScanHashBucket() to get at the contents of
     * the hash table.  -cim 6/9/91
     */
    {
        HashState  *hashstate = (HashState *) innerPlanState(hjstate);
        TupleTableSlot *slot = hashstate->ps.ps_ResultTupleSlot;

        hjstate->hj_HashTupleSlot = slot;
    }

    /*
     * initialize tuple type and projection info
     */
    ExecAssignResultTypeFromTL(&hjstate->js.ps);
    ExecAssignProjectionInfo(&hjstate->js.ps, NULL);

    ExecSetSlotDescriptor(hjstate->hj_OuterTupleSlot,
                          ExecGetResultType(outerPlanState(hjstate)));

    /*
     * initialize hash-specific info
     */
    hjstate->hj_HashTable = NULL;
    hjstate->hj_FirstOuterTupleSlot = NULL;

    hjstate->hj_CurHashValue = 0;
    hjstate->hj_CurBucketNo = 0;
    hjstate->hj_CurSkewBucketNo = INVALID_SKEW_BUCKET_NO;
    hjstate->hj_CurTuple = NULL;

    /*
     * Deconstruct the hash clauses into outer and inner argument values, so
     * that we can evaluate those subexpressions separately.  Also make a list
     * of the hash operator OIDs, in preparation for looking up the hash
     * functions to use.
     */
    lclauses = NIL;
    rclauses = NIL;
    hoperators = NIL;
    foreach(l, hjstate->hashclauses)
    {
        FuncExprState *fstate = (FuncExprState *) lfirst(l);
        OpExpr     *hclause;

        Assert(IsA(fstate, FuncExprState));
        hclause = (OpExpr *) fstate->xprstate.expr;
        Assert(IsA(hclause, OpExpr));
        lclauses = lappend(lclauses, linitial(fstate->args));
        rclauses = lappend(rclauses, lsecond(fstate->args));
        hoperators = lappend_oid(hoperators, hclause->opno);
    }
    hjstate->hj_OuterHashKeys = lclauses;
    hjstate->hj_InnerHashKeys = rclauses;
    hjstate->hj_HashOperators = hoperators;
    /* child Hash node needs to evaluate inner hash keys, too */
    ((HashState *) innerPlanState(hjstate))->hashkeys = rclauses;

    hjstate->js.ps.ps_TupFromTlist = false;
    hjstate->hj_JoinState = HJ_BUILD_HASHTABLE;
    hjstate->hj_MatchedOuter = false;
    hjstate->hj_OuterNotEmpty = false;

    return hjstate;
}

void ExecReScanHashJoin ( HashJoinState node  ) 

Definition at line 944 of file nodeHashjoin.c.

References PlanState::chgParam, ExecHashTableDestroy(), ExecHashTableResetMatchFlags(), ExecReScan(), HashJoinState::hj_CurBucketNo, HashJoinState::hj_CurHashValue, HashJoinState::hj_CurSkewBucketNo, HashJoinState::hj_CurTuple, HJ_FILL_INNER, HashJoinState::hj_FirstOuterTupleSlot, HashJoinState::hj_HashTable, HashJoinState::hj_JoinState, HashJoinState::hj_MatchedOuter, HashJoinState::hj_OuterNotEmpty, HashJoinState::js, PlanState::lefttree, HashJoinTableData::nbatch, NULL, JoinState::ps, PlanState::ps_TupFromTlist, and PlanState::righttree.

Referenced by ExecReScan().

{
    /*
     * In a multi-batch join, we currently have to do rescans the hard way,
     * primarily because batch temp files may have already been released. But
     * if it's a single-batch join, and there is no parameter change for the
     * inner subnode, then we can just re-use the existing hash table without
     * rebuilding it.
     */
    if (node->hj_HashTable != NULL)
    {
        if (node->hj_HashTable->nbatch == 1 &&
            node->js.ps.righttree->chgParam == NULL)
        {
            /*
             * Okay to reuse the hash table; needn't rescan inner, either.
             *
             * However, if it's a right/full join, we'd better reset the
             * inner-tuple match flags contained in the table.
             */
            if (HJ_FILL_INNER(node))
                ExecHashTableResetMatchFlags(node->hj_HashTable);

            /*
             * Also, we need to reset our state about the emptiness of the
             * outer relation, so that the new scan of the outer will update
             * it correctly if it turns out to be empty this time. (There's no
             * harm in clearing it now because ExecHashJoin won't need the
             * info.  In the other cases, where the hash table doesn't exist
             * or we are destroying it, we leave this state alone because
             * ExecHashJoin will need it the first time through.)
             */
            node->hj_OuterNotEmpty = false;

            /* ExecHashJoin can skip the BUILD_HASHTABLE step */
            node->hj_JoinState = HJ_NEED_NEW_OUTER;
        }
        else
        {
            /* must destroy and rebuild hash table */
            ExecHashTableDestroy(node->hj_HashTable);
            node->hj_HashTable = NULL;
            node->hj_JoinState = HJ_BUILD_HASHTABLE;

            /*
             * if chgParam of subnode is not null then plan will be re-scanned
             * by first ExecProcNode.
             */
            if (node->js.ps.righttree->chgParam == NULL)
                ExecReScan(node->js.ps.righttree);
        }
    }

    /* Always reset intra-tuple state */
    node->hj_CurHashValue = 0;
    node->hj_CurBucketNo = 0;
    node->hj_CurSkewBucketNo = INVALID_SKEW_BUCKET_NO;
    node->hj_CurTuple = NULL;

    node->js.ps.ps_TupFromTlist = false;
    node->hj_MatchedOuter = false;
    node->hj_FirstOuterTupleSlot = NULL;

    /*
     * if chgParam of subnode is not null then plan will be re-scanned by
     * first ExecProcNode.
     */
    if (node->js.ps.lefttree->chgParam == NULL)
        ExecReScan(node->js.ps.lefttree);
}