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Arrange for hash join to skip scanning the outer relation if it detects

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that the inner one is completely empty.  Per recent discussion.  Also some
cosmetic cleanups in nearby code.
This commit is contained in:
Tom Lane 2004-09-22 19:13:52 +00:00
parent 5d9f5c20dd
commit 9fcbe2af11
3 changed files with 27 additions and 14 deletions
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12
src/backend/executor/nodeHash.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.86 2004/08/29 04:12:31 momjian Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeHash.c,v 1.87 2004/09/22 19:13:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -32,8 +32,8 @@
/* ----------------------------------------------------------------
* ExecHash
*
* build hash table for hashjoin, all do partitioning if more
* than one batches are required.
* build hash table for hashjoin, doing partitioning if more
* than one batch is required.
* ----------------------------------------------------------------
*/
TupleTableSlot *
@ -81,6 +81,7 @@ ExecHash(HashState *node)
slot = ExecProcNode(outerNode);
if (TupIsNull(slot))
break;
hashtable->hashNonEmpty = true;
econtext->ecxt_innertuple = slot;
ExecHashTableInsert(hashtable, econtext, hashkeys);
ExecClearTuple(slot);
@ -189,7 +190,7 @@ ExecEndHash(HashState *node)
/* ----------------------------------------------------------------
* ExecHashTableCreate
*
* create a hashtable in shared memory for hashjoin.
* create an empty hashtable data structure for hashjoin.
* ----------------------------------------------------------------
*/
HashJoinTable
@ -226,12 +227,13 @@ ExecHashTableCreate(Hash *node, List *hashOperators)
* The hashtable control block is just palloc'd from the executor's
* per-query memory context.
*/
hashtable = (HashJoinTable) palloc(sizeof(HashTableData));
hashtable = (HashJoinTable) palloc(sizeof(HashJoinTableData));
hashtable->nbuckets = nbuckets;
hashtable->totalbuckets = totalbuckets;
hashtable->buckets = NULL;
hashtable->nbatch = nbatch;
hashtable->curbatch = 0;
hashtable->hashNonEmpty = false;
hashtable->innerBatchFile = NULL;
hashtable->outerBatchFile = NULL;
hashtable->innerBatchSize = NULL;

19
src/backend/executor/nodeHashjoin.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.65 2004/09/17 18:28:53 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeHashjoin.c,v 1.66 2004/09/22 19:13:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -127,6 +127,17 @@ ExecHashJoin(HashJoinState *node)
hashNode->hashtable = hashtable;
(void) ExecProcNode((PlanState *) hashNode);
/*
* If the inner relation is completely empty, and we're not doing
* an outer join, we can quit without scanning the outer relation.
*/
if (!hashtable->hashNonEmpty && node->js.jointype != JOIN_LEFT)
{
ExecHashTableDestroy(hashtable);
node->hj_HashTable = NULL;
return NULL;
}
/*
* Open temp files for outer batches, if needed. Note that file
* buffers are palloc'd in regular executor context.
@ -138,10 +149,8 @@ ExecHashJoin(HashJoinState *node)
}
/*
* Now get an outer tuple and probe into the hash table for matches
* run the hash join process
*/
outerTupleSlot = node->js.ps.ps_OuterTupleSlot;
for (;;)
{
/*
@ -226,7 +235,7 @@ ExecHashJoin(HashJoinState *node)
* Only the joinquals determine MatchedOuter status, but all
* quals must pass to actually return the tuple.
*/
if (ExecQual(joinqual, econtext, false))
if (joinqual == NIL || ExecQual(joinqual, econtext, false))
{
node->hj_MatchedOuter = true;

10
src/include/executor/hashjoin.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/executor/hashjoin.h,v 1.32 2004/08/29 04:13:06 momjian Exp $
* $PostgreSQL: pgsql/src/include/executor/hashjoin.h,v 1.33 2004/09/22 19:13:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -47,7 +47,7 @@ typedef struct HashJoinTupleData
typedef HashJoinTupleData *HashJoinTuple;
typedef struct HashTableData
typedef struct HashJoinTableData
{
int nbuckets; /* buckets in use during this batch */
int totalbuckets; /* total number of (virtual) buckets */
@ -57,6 +57,8 @@ typedef struct HashTableData
int nbatch; /* number of batches; 0 means 1-pass join */
int curbatch; /* current batch #, or 0 during 1st pass */
bool hashNonEmpty; /* did inner plan produce any rows? */
/*
* all these arrays are allocated for the life of the hash join, but
* only if nbatch > 0:
@ -90,8 +92,8 @@ typedef struct HashTableData
MemoryContext hashCxt; /* context for whole-hash-join storage */
MemoryContext batchCxt; /* context for this-batch-only storage */
} HashTableData;
} HashJoinTableData;
typedef HashTableData *HashJoinTable;
typedef HashJoinTableData *HashJoinTable;
#endif /* HASHJOIN_H */