From b79cb1eea1e33251683ffee217cbc8d6fb5e2f5f Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 28 Nov 2005 17:14:23 +0000
Subject: [PATCH] Recent changes to allow hash join to exit early given empty
input from one child or the other had a problem: they did not leave the node
in a state that ExecReScanHashJoin would understand. In particular it would
tend to fail to reset the child plans when needed. Per report from Mario
Weilguni.
---
src/backend/executor/nodeHashjoin.c | 50 ++++++++++++-----------------
1 file changed, 20 insertions(+), 30 deletions(-)
diff --git a/src/backend/executor/nodeHashjoin.c b/src/backend/executor/nodeHashjoin.c
index 86c63da4f76..ee2809a8b45 100644
--- a/src/backend/executor/nodeHashjoin.c
+++ b/src/backend/executor/nodeHashjoin.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.77 2005/11/22 18:17:10 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.78 2005/11/28 17:14:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -152,12 +152,7 @@ ExecHashJoin(HashJoinState *node)
* outer join, we can quit without scanning the outer relation.
*/
if (hashtable->totalTuples == 0 && node->js.jointype != JOIN_LEFT)
- {
- ExecHashTableDestroy(hashtable);
- node->hj_HashTable = NULL;
- node->hj_FirstOuterTupleSlot = NULL;
return NULL;
- }
/*
* need to remember whether nbatch has increased since we began
@@ -487,7 +482,6 @@ ExecEndHashJoin(HashJoinState *node)
{
ExecHashTableDestroy(node->hj_HashTable);
node->hj_HashTable = NULL;
- node->hj_FirstOuterTupleSlot = NULL;
}
/*
@@ -803,13 +797,6 @@ ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
void
ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
{
- /*
- * If we haven't yet built the hash table then we can just return; nothing
- * done yet, so nothing to undo.
- */
- if (node->hj_HashTable == NULL)
- return;
-
/*
* 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
@@ -817,24 +804,26 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
* inner subnode, then we can just re-use the existing hash table without
* rebuilding it.
*/
- if (node->hj_HashTable->nbatch == 1 &&
- ((PlanState *) node)->righttree->chgParam == NULL)
- {
- /* okay to reuse the hash table; needn't rescan inner, either */
- }
- else
+ if (node->hj_HashTable != NULL)
{
- /* must destroy and rebuild hash table */
- ExecHashTableDestroy(node->hj_HashTable);
- node->hj_HashTable = NULL;
- node->hj_FirstOuterTupleSlot = NULL;
+ if (node->hj_HashTable->nbatch == 1 &&
+ ((PlanState *) node)->righttree->chgParam == NULL)
+ {
+ /* okay to reuse the hash table; needn't rescan inner, either */
+ }
+ else
+ {
+ /* must destroy and rebuild hash table */
+ ExecHashTableDestroy(node->hj_HashTable);
+ node->hj_HashTable = NULL;
- /*
- * if chgParam of subnode is not null then plan will be re-scanned by
- * first ExecProcNode.
- */
- if (((PlanState *) node)->righttree->chgParam == NULL)
- ExecReScan(((PlanState *) node)->righttree, exprCtxt);
+ /*
+ * if chgParam of subnode is not null then plan will be re-scanned
+ * by first ExecProcNode.
+ */
+ if (((PlanState *) node)->righttree->chgParam == NULL)
+ ExecReScan(((PlanState *) node)->righttree, exprCtxt);
+ }
}
/* Always reset intra-tuple state */
@@ -846,6 +835,7 @@ ExecReScanHashJoin(HashJoinState *node, ExprContext *exprCtxt)
node->js.ps.ps_TupFromTlist = false;
node->hj_NeedNewOuter = true;
node->hj_MatchedOuter = false;
+ node->hj_FirstOuterTupleSlot = NULL;
/*
* if chgParam of subnode is not null then plan will be re-scanned by
--
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