From 118461114e14f4fac5103df173df192771b5befc Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 15 Aug 2008 19:20:42 +0000
Subject: [PATCH] Performance fix for new anti-join code in nodeMergejoin.c:
after finding a match in antijoin mode, we should advance to next outer tuple
not next inner. We know we don't want to return this outer tuple, and there
is no point in advancing over matching inner tuples now, because we'd just
have to do it again if the next outer tuple has the same merge key. This
makes a noticeable difference if there are lots of duplicate keys in both
inputs.
Similarly, after finding a match in semijoin mode, arrange to advance to
the next outer tuple after returning the current match; or immediately,
if it fails the extra quals. The rationale is the same. (This is a
performance bug in existing releases; perhaps worth back-patching? The
planner tries to avoid using mergejoin with lots of duplicates, so it may
not be a big issue in practice.)
Nestloop and hash got this right to start with, but I made some cosmetic
adjustments there to make the corresponding bits of logic look more similar.
---
src/backend/executor/nodeHashjoin.c | 50 +++++++++++++---------------
src/backend/executor/nodeMergejoin.c | 24 +++++++------
src/backend/executor/nodeNestloop.c | 47 +++++++++++++-------------
3 files changed, 62 insertions(+), 59 deletions(-)
diff --git a/src/backend/executor/nodeHashjoin.c b/src/backend/executor/nodeHashjoin.c
index 837837bece0..4534845b527 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 1.94 2008/08/14 18:47:58 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.95 2008/08/15 19:20:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -264,36 +264,34 @@ ExecHashJoin(HashJoinState *node)
node->hj_NeedNewOuter = true;
break; /* out of loop over hash bucket */
}
- else
+
+ /*
+ * 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_NeedNewOuter = true;
+
+ if (otherqual == NIL || ExecQual(otherqual, econtext, false))
{
- /*
- * 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_NeedNewOuter = true;
-
- if (otherqual == NIL || ExecQual(otherqual, econtext, false))
- {
- TupleTableSlot *result;
+ TupleTableSlot *result;
- result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
+ result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
- if (isDone != ExprEndResult)
- {
- node->js.ps.ps_TupFromTlist =
- (isDone == ExprMultipleResult);
- return result;
- }
+ if (isDone != ExprEndResult)
+ {
+ node->js.ps.ps_TupFromTlist =
+ (isDone == ExprMultipleResult);
+ return result;
}
-
- /*
- * If semijoin and we didn't return the tuple, we're still
- * done with this outer tuple.
- */
- if (node->js.jointype == JOIN_SEMI)
- break; /* out of loop over hash bucket */
}
+
+ /*
+ * If semijoin and we didn't return the tuple, we're still
+ * done with this outer tuple.
+ */
+ if (node->js.jointype == JOIN_SEMI)
+ break; /* out of loop over hash bucket */
}
}
diff --git a/src/backend/executor/nodeMergejoin.c b/src/backend/executor/nodeMergejoin.c
index e9deb5c8da7..d460349ad45 100644
--- a/src/backend/executor/nodeMergejoin.c
+++ b/src/backend/executor/nodeMergejoin.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.92 2008/08/14 18:47:58 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.93 2008/08/15 19:20:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -757,15 +757,9 @@ ExecMergeJoin(MergeJoinState *node)
innerTupleSlot = node->mj_InnerTupleSlot;
econtext->ecxt_innertuple = innerTupleSlot;
- if (node->js.jointype == JOIN_SEMI &&
- node->mj_MatchedOuter)
- qualResult = false;
- else
- {
- qualResult = (joinqual == NIL ||
- ExecQual(joinqual, econtext, false));
- MJ_DEBUG_QUAL(joinqual, qualResult);
- }
+ qualResult = (joinqual == NIL ||
+ ExecQual(joinqual, econtext, false));
+ MJ_DEBUG_QUAL(joinqual, qualResult);
if (qualResult)
{
@@ -774,7 +768,17 @@ ExecMergeJoin(MergeJoinState *node)
/* In an antijoin, we never return a matched tuple */
if (node->js.jointype == JOIN_ANTI)
+ {
+ node->mj_JoinState = EXEC_MJ_NEXTOUTER;
break;
+ }
+
+ /*
+ * 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->mj_JoinState = EXEC_MJ_NEXTOUTER;
qualResult = (otherqual == NIL ||
ExecQual(otherqual, econtext, false));
diff --git a/src/backend/executor/nodeNestloop.c b/src/backend/executor/nodeNestloop.c
index c6a33228582..27e3582649e 100644
--- a/src/backend/executor/nodeNestloop.c
+++ b/src/backend/executor/nodeNestloop.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/nodeNestloop.c,v 1.47 2008/08/14 18:47:58 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeNestloop.c,v 1.48 2008/08/15 19:20:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -226,35 +226,36 @@ ExecNestLoop(NestLoopState *node)
/* In an antijoin, we never return a matched tuple */
if (node->js.jointype == JOIN_ANTI)
+ {
node->nl_NeedNewOuter = true;
- else
+ continue; /* return to top of loop */
+ }
+
+ /*
+ * 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->nl_NeedNewOuter = true;
+
+ if (otherqual == NIL || ExecQual(otherqual, econtext, false))
{
/*
- * In a semijoin, we'll consider returning the first match,
- * but after that we're done with this outer tuple.
+ * qualification was satisfied so we project and return the
+ * slot containing the result tuple using ExecProject().
*/
- if (node->js.jointype == JOIN_SEMI)
- node->nl_NeedNewOuter = true;
- if (otherqual == NIL || ExecQual(otherqual, econtext, false))
- {
- /*
- * qualification was satisfied so we project and return
- * the slot containing the result tuple using
- * ExecProject().
- */
- TupleTableSlot *result;
- ExprDoneCond isDone;
+ TupleTableSlot *result;
+ ExprDoneCond isDone;
- ENL1_printf("qualification succeeded, projecting tuple");
+ ENL1_printf("qualification succeeded, projecting tuple");
- result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
+ result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
- if (isDone != ExprEndResult)
- {
- node->js.ps.ps_TupFromTlist =
- (isDone == ExprMultipleResult);
- return result;
- }
+ if (isDone != ExprEndResult)
+ {
+ node->js.ps.ps_TupFromTlist =
+ (isDone == ExprMultipleResult);
+ return result;
}
}
}
--
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