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Detect duplicate aggregate calls and evaluate only one copy. This

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speeds up some useful real-world cases like
SELECT x, COUNT(*) FROM t GROUP BY x HAVING COUNT(*) > 100.
This commit is contained in:
Tom Lane 2003-02-04 00:48:23 +00:00
parent ef5842b5f7
commit 85caf1784a
1 changed files with 28 additions and 3 deletions
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31
src/backend/executor/nodeAgg.c
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@ -45,7 +45,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.102 2003/01/10 23:54:24 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.103 2003/02/04 00:48:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1159,20 +1159,42 @@ ExecInitAgg(Agg *node, EState *estate)
/*
* Perform lookups of aggregate function info, and initialize the
* unchanging fields of the per-agg data
* unchanging fields of the per-agg data. We also detect duplicate
* aggregates (for example, "SELECT sum(x) ... HAVING sum(x) > 0").
* When duplicates are detected, we only make an AggStatePerAgg struct
* for the first one. The clones are simply pointed at the same result
* entry by giving them duplicate aggno values.
*/
aggno = -1;
foreach(alist, aggstate->aggs)
{
AggrefExprState *aggrefstate = (AggrefExprState *) lfirst(alist);
Aggref *aggref = (Aggref *) aggrefstate->xprstate.expr;
AggStatePerAgg peraggstate = &peragg[++aggno];
AggStatePerAgg peraggstate;
HeapTuple aggTuple;
Form_pg_aggregate aggform;
AclResult aclresult;
Oid transfn_oid,
finalfn_oid;
Datum textInitVal;
int i;
/* Look for a previous duplicate aggregate */
for (i = 0; i <= aggno; i++)
{
if (equal(aggref, peragg[i].aggref) &&
!contain_volatile_functions((Node *) aggref))
break;
}
if (i <= aggno)
{
/* Found a match to an existing entry, so just mark it */
aggrefstate->aggno = i;
continue;
}
/* Nope, so assign a new PerAgg record */
peraggstate = &peragg[++aggno];
/* Mark Aggref state node with assigned index in the result array */
aggrefstate->aggno = aggno;
@ -1271,6 +1293,9 @@ ExecInitAgg(Agg *node, EState *estate)
ReleaseSysCache(aggTuple);
}
/* Update numaggs to match number of unique aggregates found */
aggstate->numaggs = aggno + 1;
return aggstate;
}