Support ORDER BY within aggregate function calls, at long last providing a

non-kluge method for controlling the order in which values are fed to an
aggregate function.  At the same time eliminate the old implementation
restriction that DISTINCT was only supported for single-argument aggregates.

Possibly release-notable behavioral change: formerly, agg(DISTINCT x)
dropped null values of x unconditionally.  Now, it does so only if the
agg transition function is strict; otherwise nulls are treated as DISTINCT
normally would, ie, you get one copy.

Andrew Gierth, reviewed by Hitoshi Harada

1 files changed, 10 insertions, 9 deletions

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index a5c343298e..56b432c9bb 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.280 2009/12/14 02:15:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.281 2009/12/15 17:57:47 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -471,21 +471,22 @@ count_agg_clauses_walker(Node *node, AggClauseCounts *counts)
 		HeapTuple	aggTuple;
 		Form_pg_aggregate aggform;
 		Oid			aggtranstype;
-		int			i;
 		ListCell   *l;
 
 		Assert(aggref->agglevelsup == 0);
 		counts->numAggs++;
-		if (aggref->aggdistinct)
-			counts->numDistinctAggs++;
+		if (aggref->aggorder != NIL || aggref->aggdistinct != NIL)
+			counts->numOrderedAggs++;
 
-		/* extract argument types */
-		numArguments = list_length(aggref->args);
-		inputTypes = (Oid *) palloc(sizeof(Oid) * numArguments);
-		i = 0;
+		/* extract argument types (ignoring any ORDER BY expressions) */
+		inputTypes = (Oid *) palloc(sizeof(Oid) * list_length(aggref->args));
+		numArguments = 0;
 		foreach(l, aggref->args)
 		{
-			inputTypes[i++] = exprType((Node *) lfirst(l));
+			TargetEntry *tle = (TargetEntry *) lfirst(l);
+
+			if (!tle->resjunk)
+				inputTypes[numArguments++] = exprType((Node *) tle->expr);
 		}
 
 		/* fetch aggregate transition datatype from pg_aggregate */