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https://git.postgresql.org/git/postgresql.git
synced 2025-03-07 19:47:50 +08:00
The original patch to avoid building a hash join's hashtable when the
outer relation is empty did not work, per test case from Patrick Welche. It tried to use nodeHashjoin.c's high-level mechanisms for fetching an outer-relation tuple, but that code expected the hash table to be filled already. As patched, the code failed in corner cases such as having no outer-relation tuples for the first hash batch. Revert and rewrite.
This commit is contained in:
Tom Lane
parent
dd102d3683
commit
e990b9ce23
@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.94 2005/06/15 07:27:44 neilc Exp $
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* $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.95 2005/09/25 19:37:34 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -37,22 +37,14 @@ static void ExecHashIncreaseNumBatches(HashJoinTable hashtable);
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/* ----------------------------------------------------------------
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* ExecHash
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*
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* produce the first tuple from our child node (and _only_ the
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* first tuple). This is of limited general use -- it does not
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* hash its output, and produces only a single tuple. It is
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* provided so that hash join can probe the inner hash input to
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* determine whether it is empty without needing to build the
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* entire hash table first, which is what MultiExecHash() would
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* do.
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* stub for pro forma compliance
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* ----------------------------------------------------------------
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*/
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TupleTableSlot *
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ExecHash(HashState *node)
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{
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if (TupIsNull(node->firstTuple))
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node->firstTuple = ExecProcNode(outerPlanState(node));
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return node->firstTuple;
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elog(ERROR, "Hash node does not support ExecProcNode call convention");
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return NULL;
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}
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/* ----------------------------------------------------------------
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@ -71,7 +63,6 @@ MultiExecHash(HashState *node)
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TupleTableSlot *slot;
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ExprContext *econtext;
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uint32 hashvalue;
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bool cleared_first_tuple = false;
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/* must provide our own instrumentation support */
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if (node->ps.instrument)
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@ -94,19 +85,9 @@ MultiExecHash(HashState *node)
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*/
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for (;;)
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{
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/* use and clear the tuple produced by ExecHash(), if any */
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if (!TupIsNull(node->firstTuple))
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{
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slot = node->firstTuple;
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node->firstTuple = NULL;
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cleared_first_tuple = true;
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}
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else
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{
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slot = ExecProcNode(outerNode);
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if (TupIsNull(slot))
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break;
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}
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slot = ExecProcNode(outerNode);
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if (TupIsNull(slot))
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break;
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hashtable->totalTuples += 1;
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/* We have to compute the hash value */
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econtext->ecxt_innertuple = slot;
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@ -116,19 +97,7 @@ MultiExecHash(HashState *node)
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/* must provide our own instrumentation support */
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if (node->ps.instrument)
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{
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/*
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* XXX: kludge -- if ExecHash() was invoked, we've already
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* included the tuple that it produced in the row output count
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* for this node, so subtract 1 from the # of hashed tuples.
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*/
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if (cleared_first_tuple)
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InstrStopNodeMulti(node->ps.instrument,
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hashtable->totalTuples - 1);
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else
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InstrStopNodeMulti(node->ps.instrument,
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hashtable->totalTuples);
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}
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InstrStopNodeMulti(node->ps.instrument, hashtable->totalTuples);
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/*
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* We do not return the hash table directly because it's not a subtype
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@ -161,7 +130,6 @@ ExecInitHash(Hash *node, EState *estate)
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hashstate->ps.state = estate;
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hashstate->hashtable = NULL;
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hashstate->hashkeys = NIL; /* will be set by parent HashJoin */
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hashstate->firstTuple = NULL;
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/*
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* Miscellaneous initialization
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@ -221,8 +189,6 @@ ExecEndHash(HashState *node)
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{
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PlanState *outerPlan;
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node->firstTuple = NULL;
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/*
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* free exprcontext
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*/
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@ -864,8 +830,6 @@ ExecHashTableReset(HashJoinTable hashtable)
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void
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ExecReScanHash(HashState *node, ExprContext *exprCtxt)
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{
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node->firstTuple = NULL;
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/*
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* if chgParam of subnode is not null then plan will be re-scanned by
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* first ExecProcNode.
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.72 2005/06/15 07:27:44 neilc Exp $
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* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.73 2005/09/25 19:37:34 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -31,7 +31,7 @@ static TupleTableSlot *ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
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uint32 *hashvalue,
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TupleTableSlot *tupleSlot);
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static int ExecHashJoinNewBatch(HashJoinState *hjstate);
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static TupleTableSlot *ExecHashJoinReadOuterPlan(HashJoinState *hjstate);
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/* ----------------------------------------------------------------
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* ExecHashJoin
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@ -57,6 +57,8 @@ ExecHashJoin(HashJoinState *node)
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HashJoinTable hashtable;
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HeapTuple curtuple;
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TupleTableSlot *outerTupleSlot;
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uint32 hashvalue;
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int batchno;
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/*
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* get information from HashJoin node
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@ -105,69 +107,57 @@ ExecHashJoin(HashJoinState *node)
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*/
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ResetExprContext(econtext);
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/*
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* if this is the first call, build the hash table for inner relation
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*/
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if (hashtable == NULL)
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{
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/*
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* This is the first call to the node. When _either_ of the
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* hash join inputs are empty, we want to avoid doing
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* unnecessary work (e.g. building the hash table for the
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* inner join relation). We therefore read a single tuple from
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* both inputs before proceeding further. We choose which
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* input to probe first based on the startup cost of the plan
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* node.
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* If the outer relation is completely empty, we can quit without
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* building the hash table. However, for an inner join it is only
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* a win to check this when the outer relation's startup cost is less
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* than the projected cost of building the hash table. Otherwise
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* it's best to build the hash table first and see if the inner
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* relation is empty. (When it's an outer join, we should always
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* make this check, since we aren't going to be able to skip the
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* join on the strength of an empty inner relation anyway.)
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*
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* Note that if we're executing an outer join and the inner
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* relation is empty, we still have work to do.
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* The only way to make the check is to try to fetch a tuple from
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* the outer plan node. If we succeed, we have to stash it away
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* for later consumption by ExecHashJoinOuterGetTuple.
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*/
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/* Consider probing the inner relation first */
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if (hashNode->ps.plan->startup_cost <= outerNode->plan->startup_cost &&
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node->js.jointype != JOIN_LEFT)
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if (outerNode->plan->startup_cost < hashNode->ps.plan->total_cost ||
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node->js.jointype == JOIN_LEFT)
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{
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/*
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* ExecHash() lets us get a single tuple from the inner
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* relation without building the entire hash table
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*/
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TupleTableSlot *tup = ExecProcNode(&hashNode->ps);
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if (TupIsNull(tup))
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node->hj_FirstOuterTupleSlot = ExecProcNode(outerNode);
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if (TupIsNull(node->hj_FirstOuterTupleSlot))
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return NULL;
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}
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else
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node->hj_FirstOuterTupleSlot = NULL;
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/*
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* Before we can check the outer relation, we need to build
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* the hash table. This is somewhat a waste of time if the
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* outer relation is empty, but it would be awkward to avoid.
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* create the hash table
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*/
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hashtable = ExecHashTableCreate((Hash *) hashNode->ps.plan,
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node->hj_HashOperators);
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node->hj_HashTable = hashtable;
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hashNode->hashtable = hashtable;
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/* Now check the outer relation */
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outerTupleSlot = ExecHashJoinReadOuterPlan(node);
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if (TupIsNull(outerTupleSlot))
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{
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ExecHashTableDestroy(node->hj_HashTable);
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node->hj_HashTable = NULL;
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return NULL;
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}
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/*
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* Okay, we can't avoid it, so execute the Hash node to build
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* the hash table
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* execute the Hash node, to build the hash table
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*/
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hashNode->hashtable = hashtable;
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(void) MultiExecProcNode((PlanState *) hashNode);
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/*
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* If the inner relation is empty but its startup cost was
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* less than the outer relation's startup cost, we can arrive
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* here -- we're done unless this is an outer join
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* If the inner relation is completely empty, and we're not doing
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* an outer join, we can quit without scanning the outer relation.
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*/
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if (hashtable->totalTuples == 0 && node->js.jointype != JOIN_LEFT)
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{
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ExecHashTableDestroy(node->hj_HashTable);
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ExecHashTableDestroy(hashtable);
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node->hj_HashTable = NULL;
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node->hj_FirstOuterTupleSlot = NULL;
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return NULL;
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}
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@ -188,9 +178,46 @@ ExecHashJoin(HashJoinState *node)
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*/
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if (node->hj_NeedNewOuter)
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{
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outerTupleSlot = ExecHashJoinReadOuterPlan(node);
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outerTupleSlot = ExecHashJoinOuterGetTuple(outerNode,
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node,
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&hashvalue);
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if (TupIsNull(outerTupleSlot))
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return NULL; /* end of join */
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{
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/* end of join */
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return NULL;
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}
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node->js.ps.ps_OuterTupleSlot = outerTupleSlot;
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econtext->ecxt_outertuple = outerTupleSlot;
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node->hj_NeedNewOuter = false;
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node->hj_MatchedOuter = false;
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/*
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* now we have an outer tuple, find the corresponding bucket
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* for this tuple from the hash table
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*/
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node->hj_CurHashValue = hashvalue;
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ExecHashGetBucketAndBatch(hashtable, hashvalue,
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&node->hj_CurBucketNo, &batchno);
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node->hj_CurTuple = NULL;
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/*
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* Now we've got an outer tuple and the corresponding hash
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* bucket, but this tuple may not belong to the current batch.
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*/
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if (batchno != hashtable->curbatch)
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{
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/*
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* Need to postpone this outer tuple to a later batch.
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* Save it in the corresponding outer-batch file.
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*/
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Assert(batchno > hashtable->curbatch);
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ExecHashJoinSaveTuple(ExecFetchSlotTuple(outerTupleSlot),
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hashvalue,
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&hashtable->outerBatchFile[batchno]);
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node->hj_NeedNewOuter = true;
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continue; /* loop around for a new outer tuple */
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}
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}
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/*
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@ -400,6 +427,7 @@ ExecInitHashJoin(HashJoin *node, EState *estate)
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* initialize hash-specific info
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*/
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hjstate->hj_HashTable = NULL;
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hjstate->hj_FirstOuterTupleSlot = NULL;
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hjstate->hj_CurHashValue = 0;
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hjstate->hj_CurBucketNo = 0;
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@ -464,6 +492,7 @@ ExecEndHashJoin(HashJoinState *node)
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{
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ExecHashTableDestroy(node->hj_HashTable);
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node->hj_HashTable = NULL;
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node->hj_FirstOuterTupleSlot = NULL;
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}
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/*
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@ -485,79 +514,6 @@ ExecEndHashJoin(HashJoinState *node)
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ExecEndNode(innerPlanState(node));
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}
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/*
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* ExecHashJoinReadOuterPlan
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*
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* do all the work necessary to produce the next tuple from the
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* outer hash join relation that is in the current batch. Returns
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* NULL if there are no more tuples in the outer relation.
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*/
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static TupleTableSlot *
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ExecHashJoinReadOuterPlan(HashJoinState *hjstate)
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{
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PlanState *outerNode;
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ExprContext *econtext;
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HashJoinTable hashtable;
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outerNode = outerPlanState(hjstate);
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econtext = hjstate->js.ps.ps_ExprContext;
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hashtable = hjstate->hj_HashTable;
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for (;;)
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{
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TupleTableSlot *result;
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uint32 hashvalue;
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int batchno;
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result = ExecHashJoinOuterGetTuple(outerNode,
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hjstate,
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&hashvalue);
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if (TupIsNull(result))
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{
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/* end of join */
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return NULL;
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}
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hjstate->js.ps.ps_OuterTupleSlot = result;
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econtext->ecxt_outertuple = result;
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hjstate->hj_NeedNewOuter = false;
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hjstate->hj_MatchedOuter = false;
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/*
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* now we have an outer tuple, find the corresponding bucket
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* for this tuple from the hash table
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*/
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hjstate->hj_CurHashValue = hashvalue;
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ExecHashGetBucketAndBatch(hashtable, hashvalue,
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&hjstate->hj_CurBucketNo, &batchno);
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hjstate->hj_CurTuple = NULL;
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/*
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* Now we've got an outer tuple and the corresponding hash
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* bucket, but this tuple may not belong to the current batch.
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*/
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if (batchno != hashtable->curbatch)
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{
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/*
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* Need to postpone this outer tuple to a later batch.
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* Save it in the corresponding outer-batch file.
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*/
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Assert(batchno > hashtable->curbatch);
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ExecHashJoinSaveTuple(ExecFetchSlotTuple(result),
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hashvalue,
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&hashtable->outerBatchFile[batchno]);
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hjstate->hj_NeedNewOuter = true;
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continue; /* Get the next outer tuple */
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}
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/*
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* Otherwise, we have a tuple in the current batch, so we're
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* done
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*/
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return result;
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}
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}
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/*
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* ExecHashJoinOuterGetTuple
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*
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@ -580,7 +536,15 @@ ExecHashJoinOuterGetTuple(PlanState *outerNode,
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if (curbatch == 0)
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{ /* if it is the first pass */
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slot = ExecProcNode(outerNode);
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/*
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* Check to see if first outer tuple was already fetched by
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* ExecHashJoin() and not used yet.
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*/
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slot = hjstate->hj_FirstOuterTupleSlot;
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if (!TupIsNull(slot))
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hjstate->hj_FirstOuterTupleSlot = NULL;
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else
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slot = ExecProcNode(outerNode);
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if (!TupIsNull(slot))
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{
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/*
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@ -840,6 +804,7 @@ ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
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return ExecStoreTuple(heapTuple, tupleSlot, InvalidBuffer, true);
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}
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void
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ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
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{
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@ -867,6 +832,7 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
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/* must destroy and rebuild hash table */
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ExecHashTableDestroy(node->hj_HashTable);
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node->hj_HashTable = NULL;
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node->hj_FirstOuterTupleSlot = NULL;
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/*
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* if chgParam of subnode is not null then plan will be re-scanned
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.137 2005/08/01 20:31:15 tgl Exp $
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* $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.138 2005/09/25 19:37:35 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1097,6 +1097,7 @@ typedef struct MergeJoinState
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* hj_OuterTupleSlot tuple slot for outer tuples
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* hj_HashTupleSlot tuple slot for hashed tuples
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* hj_NullInnerTupleSlot prepared null tuple for left outer joins
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* hj_FirstOuterTupleSlot first tuple retrieved from outer plan
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* hj_NeedNewOuter true if need new outer tuple on next call
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* hj_MatchedOuter true if found a join match for current outer
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* ----------------
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@ -1120,6 +1121,7 @@ typedef struct HashJoinState
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TupleTableSlot *hj_OuterTupleSlot;
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TupleTableSlot *hj_HashTupleSlot;
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TupleTableSlot *hj_NullInnerTupleSlot;
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TupleTableSlot *hj_FirstOuterTupleSlot;
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bool hj_NeedNewOuter;
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bool hj_MatchedOuter;
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} HashJoinState;
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@ -1232,7 +1234,6 @@ typedef struct HashState
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HashJoinTable hashtable; /* hash table for the hashjoin */
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List *hashkeys; /* list of ExprState nodes */
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/* hashkeys is same as parent's hj_InnerHashKeys */
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TupleTableSlot *firstTuple; /* tuple produced by ExecHash() */
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} HashState;
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/* ----------------
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