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Commit1184611

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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 inadvancing over matching inner tuples now, because we'd just have to do itagain if the next outer tuple has the same merge key. This makes a noticeabledifference if there are lots of duplicate keys in both inputs.Similarly, after finding a match in semijoin mode, arrange to advance tothe next outer tuple after returning the current match; or immediately,if it fails the extra quals. The rationale is the same. (This is aperformance bug in existing releases; perhaps worth back-patching? Theplanner tries to avoid using mergejoin with lots of duplicates, so it maynot be a big issue in practice.)Nestloop and hash got this right to start with, but I made some cosmeticadjustments there to make the corresponding bits of logic look more similar.
1 parent5b8eb2b commit1184611

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3 files changed

+62
-59
lines changed

3 files changed

+62
-59
lines changed

‎src/backend/executor/nodeHashjoin.c

Lines changed: 24 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.94 2008/08/14 18:47:58 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.95 2008/08/15 19:20:42 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -264,36 +264,34 @@ ExecHashJoin(HashJoinState *node)
264264
node->hj_NeedNewOuter= true;
265265
break;/* out of loop over hash bucket */
266266
}
267-
else
267+
268+
/*
269+
* In a semijoin, we'll consider returning the first match,
270+
* but after that we're done with this outer tuple.
271+
*/
272+
if (node->js.jointype==JOIN_SEMI)
273+
node->hj_NeedNewOuter= true;
274+
275+
if (otherqual==NIL||ExecQual(otherqual,econtext, false))
268276
{
269-
/*
270-
* In a semijoin, we'll consider returning the first match,
271-
* but after that we're done with this outer tuple.
272-
*/
273-
if (node->js.jointype==JOIN_SEMI)
274-
node->hj_NeedNewOuter= true;
275-
276-
if (otherqual==NIL||ExecQual(otherqual,econtext, false))
277-
{
278-
TupleTableSlot*result;
277+
TupleTableSlot*result;
279278

280-
result=ExecProject(node->js.ps.ps_ProjInfo,&isDone);
279+
result=ExecProject(node->js.ps.ps_ProjInfo,&isDone);
281280

282-
if (isDone!=ExprEndResult)
283-
{
284-
node->js.ps.ps_TupFromTlist=
285-
(isDone==ExprMultipleResult);
286-
returnresult;
287-
}
281+
if (isDone!=ExprEndResult)
282+
{
283+
node->js.ps.ps_TupFromTlist=
284+
(isDone==ExprMultipleResult);
285+
returnresult;
288286
}
289-
290-
/*
291-
* If semijoin and we didn't return the tuple, we're still
292-
* done with this outer tuple.
293-
*/
294-
if (node->js.jointype==JOIN_SEMI)
295-
break;/* out of loop over hash bucket */
296287
}
288+
289+
/*
290+
* If semijoin and we didn't return the tuple, we're still
291+
* done with this outer tuple.
292+
*/
293+
if (node->js.jointype==JOIN_SEMI)
294+
break;/* out of loop over hash bucket */
297295
}
298296
}
299297

‎src/backend/executor/nodeMergejoin.c

Lines changed: 14 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.92 2008/08/14 18:47:58 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.93 2008/08/15 19:20:42 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -757,15 +757,9 @@ ExecMergeJoin(MergeJoinState *node)
757757
innerTupleSlot=node->mj_InnerTupleSlot;
758758
econtext->ecxt_innertuple=innerTupleSlot;
759759

760-
if (node->js.jointype==JOIN_SEMI&&
761-
node->mj_MatchedOuter)
762-
qualResult= false;
763-
else
764-
{
765-
qualResult= (joinqual==NIL||
766-
ExecQual(joinqual,econtext, false));
767-
MJ_DEBUG_QUAL(joinqual,qualResult);
768-
}
760+
qualResult= (joinqual==NIL||
761+
ExecQual(joinqual,econtext, false));
762+
MJ_DEBUG_QUAL(joinqual,qualResult);
769763

770764
if (qualResult)
771765
{
@@ -774,7 +768,17 @@ ExecMergeJoin(MergeJoinState *node)
774768

775769
/* In an antijoin, we never return a matched tuple */
776770
if (node->js.jointype==JOIN_ANTI)
771+
{
772+
node->mj_JoinState=EXEC_MJ_NEXTOUTER;
777773
break;
774+
}
775+
776+
/*
777+
* In a semijoin, we'll consider returning the first match,
778+
* but after that we're done with this outer tuple.
779+
*/
780+
if (node->js.jointype==JOIN_SEMI)
781+
node->mj_JoinState=EXEC_MJ_NEXTOUTER;
778782

779783
qualResult= (otherqual==NIL||
780784
ExecQual(otherqual,econtext, false));

‎src/backend/executor/nodeNestloop.c

Lines changed: 24 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/nodeNestloop.c,v 1.47 2008/08/14 18:47:58 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/nodeNestloop.c,v 1.48 2008/08/15 19:20:42 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -226,35 +226,36 @@ ExecNestLoop(NestLoopState *node)
226226

227227
/* In an antijoin, we never return a matched tuple */
228228
if (node->js.jointype==JOIN_ANTI)
229+
{
229230
node->nl_NeedNewOuter= true;
230-
else
231+
continue;/* return to top of loop */
232+
}
233+
234+
/*
235+
* In a semijoin, we'll consider returning the first match,
236+
* but after that we're done with this outer tuple.
237+
*/
238+
if (node->js.jointype==JOIN_SEMI)
239+
node->nl_NeedNewOuter= true;
240+
241+
if (otherqual==NIL||ExecQual(otherqual,econtext, false))
231242
{
232243
/*
233-
*In a semijoin, we'll consider returning the first match,
234-
*but after that we're done with this outer tuple.
244+
*qualification was satisfied so we project and return the
245+
*slot containing the result tuple using ExecProject().
235246
*/
236-
if (node->js.jointype==JOIN_SEMI)
237-
node->nl_NeedNewOuter= true;
238-
if (otherqual==NIL||ExecQual(otherqual,econtext, false))
239-
{
240-
/*
241-
* qualification was satisfied so we project and return
242-
* the slot containing the result tuple using
243-
* ExecProject().
244-
*/
245-
TupleTableSlot*result;
246-
ExprDoneCondisDone;
247+
TupleTableSlot*result;
248+
ExprDoneCondisDone;
247249

248-
ENL1_printf("qualification succeeded, projecting tuple");
250+
ENL1_printf("qualification succeeded, projecting tuple");
249251

250-
result=ExecProject(node->js.ps.ps_ProjInfo,&isDone);
252+
result=ExecProject(node->js.ps.ps_ProjInfo,&isDone);
251253

252-
if (isDone!=ExprEndResult)
253-
{
254-
node->js.ps.ps_TupFromTlist=
255-
(isDone==ExprMultipleResult);
256-
returnresult;
257-
}
254+
if (isDone!=ExprEndResult)
255+
{
256+
node->js.ps.ps_TupFromTlist=
257+
(isDone==ExprMultipleResult);
258+
returnresult;
258259
}
259260
}
260261
}

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