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Commit9fcbe2a

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Arrange for hash join to skip scanning the outer relation if it detects
that the inner one is completely empty. Per recent discussion. Also somecosmetic cleanups in nearby code.
1 parent5d9f5c2 commit9fcbe2a

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3 files changed

+27
-14
lines changed

3 files changed

+27
-14
lines changed

‎src/backend/executor/nodeHash.c

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.86 2004/08/29 04:12:31 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.87 2004/09/22 19:13:49 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -32,8 +32,8 @@
3232
/* ----------------------------------------------------------------
3333
*ExecHash
3434
*
35-
*build hash table for hashjoin,all do partitioning if more
36-
*than onebatches are required.
35+
*build hash table for hashjoin,doing partitioning if more
36+
*than onebatch is required.
3737
* ----------------------------------------------------------------
3838
*/
3939
TupleTableSlot*
@@ -81,6 +81,7 @@ ExecHash(HashState *node)
8181
slot=ExecProcNode(outerNode);
8282
if (TupIsNull(slot))
8383
break;
84+
hashtable->hashNonEmpty= true;
8485
econtext->ecxt_innertuple=slot;
8586
ExecHashTableInsert(hashtable,econtext,hashkeys);
8687
ExecClearTuple(slot);
@@ -189,7 +190,7 @@ ExecEndHash(HashState *node)
189190
/* ----------------------------------------------------------------
190191
*ExecHashTableCreate
191192
*
192-
*createahashtablein shared memory for hashjoin.
193+
*createan emptyhashtabledata structure for hashjoin.
193194
* ----------------------------------------------------------------
194195
*/
195196
HashJoinTable
@@ -226,12 +227,13 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
226227
* The hashtable control block is just palloc'd from the executor's
227228
* per-query memory context.
228229
*/
229-
hashtable= (HashJoinTable)palloc(sizeof(HashTableData));
230+
hashtable= (HashJoinTable)palloc(sizeof(HashJoinTableData));
230231
hashtable->nbuckets=nbuckets;
231232
hashtable->totalbuckets=totalbuckets;
232233
hashtable->buckets=NULL;
233234
hashtable->nbatch=nbatch;
234235
hashtable->curbatch=0;
236+
hashtable->hashNonEmpty= false;
235237
hashtable->innerBatchFile=NULL;
236238
hashtable->outerBatchFile=NULL;
237239
hashtable->innerBatchSize=NULL;

‎src/backend/executor/nodeHashjoin.c

Lines changed: 14 additions & 5 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 1.65 2004/09/17 18:28:53 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.66 2004/09/22 19:13:49 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -127,6 +127,17 @@ ExecHashJoin(HashJoinState *node)
127127
hashNode->hashtable=hashtable;
128128
(void)ExecProcNode((PlanState*)hashNode);
129129

130+
/*
131+
* If the inner relation is completely empty, and we're not doing
132+
* an outer join, we can quit without scanning the outer relation.
133+
*/
134+
if (!hashtable->hashNonEmpty&&node->js.jointype!=JOIN_LEFT)
135+
{
136+
ExecHashTableDestroy(hashtable);
137+
node->hj_HashTable=NULL;
138+
returnNULL;
139+
}
140+
130141
/*
131142
* Open temp files for outer batches, if needed. Note that file
132143
* buffers are palloc'd in regular executor context.
@@ -138,10 +149,8 @@ ExecHashJoin(HashJoinState *node)
138149
}
139150

140151
/*
141-
*Now get an outer tuple and probe intothe hashtable for matches
152+
*runthe hashjoin process
142153
*/
143-
outerTupleSlot=node->js.ps.ps_OuterTupleSlot;
144-
145154
for (;;)
146155
{
147156
/*
@@ -226,7 +235,7 @@ ExecHashJoin(HashJoinState *node)
226235
* Only the joinquals determine MatchedOuter status, but all
227236
* quals must pass to actually return the tuple.
228237
*/
229-
if (ExecQual(joinqual,econtext, false))
238+
if (joinqual==NIL||ExecQual(joinqual,econtext, false))
230239
{
231240
node->hj_MatchedOuter= true;
232241

‎src/include/executor/hashjoin.h

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/executor/hashjoin.h,v 1.32 2004/08/29 04:13:06 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/executor/hashjoin.h,v 1.33 2004/09/22 19:13:52 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -47,7 +47,7 @@ typedef struct HashJoinTupleData
4747

4848
typedefHashJoinTupleData*HashJoinTuple;
4949

50-
typedefstructHashTableData
50+
typedefstructHashJoinTableData
5151
{
5252
intnbuckets;/* buckets in use during this batch */
5353
inttotalbuckets;/* total number of (virtual) buckets */
@@ -57,6 +57,8 @@ typedef struct HashTableData
5757
intnbatch;/* number of batches; 0 means 1-pass join */
5858
intcurbatch;/* current batch #, or 0 during 1st pass */
5959

60+
boolhashNonEmpty;/* did inner plan produce any rows? */
61+
6062
/*
6163
* all these arrays are allocated for the life of the hash join, but
6264
* only if nbatch > 0:
@@ -90,8 +92,8 @@ typedef struct HashTableData
9092

9193
MemoryContexthashCxt;/* context for whole-hash-join storage */
9294
MemoryContextbatchCxt;/* context for this-batch-only storage */
93-
}HashTableData;
95+
}HashJoinTableData;
9496

95-
typedefHashTableData*HashJoinTable;
97+
typedefHashJoinTableData*HashJoinTable;
9698

9799
#endif/* HASHJOIN_H */

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