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, 20 insertions, 8 deletions

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 71e614d7004..856a2f75806 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.316 2009/12/07 05:22:22 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.317 2009/12/15 17:57:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -5442,32 +5442,44 @@ get_agg_expr(Aggref *aggref, deparse_context *context)
 {
 	StringInfo	buf = context->buf;
 	Oid			argtypes[FUNC_MAX_ARGS];
+	List       *arglist;
 	int			nargs;
 	ListCell   *l;
 
-	if (list_length(aggref->args) > FUNC_MAX_ARGS)
-		ereport(ERROR,
-				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
-				 errmsg("too many arguments")));
+	/* Extract the regular arguments, ignoring resjunk stuff for the moment */
+	arglist = NIL;
 	nargs = 0;
 	foreach(l, aggref->args)
 	{
-		Node   *arg = (Node *) lfirst(l);
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
+		Node   *arg = (Node *) tle->expr;
 
 		Assert(!IsA(arg, NamedArgExpr));
+		if (tle->resjunk)
+			continue;
+		if (nargs >= FUNC_MAX_ARGS)				/* paranoia */
+			ereport(ERROR,
+					(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
+					 errmsg("too many arguments")));
 		argtypes[nargs] = exprType(arg);
+		arglist = lappend(arglist, arg);
 		nargs++;
 	}
 
 	appendStringInfo(buf, "%s(%s",
 					 generate_function_name(aggref->aggfnoid, nargs,
 											NIL, argtypes, NULL),
-					 aggref->aggdistinct ? "DISTINCT " : "");
+					 (aggref->aggdistinct != NIL) ? "DISTINCT " : "");
 	/* aggstar can be set only in zero-argument aggregates */
 	if (aggref->aggstar)
 		appendStringInfoChar(buf, '*');
 	else
-		get_rule_expr((Node *) aggref->args, context, true);
+		get_rule_expr((Node *) arglist, context, true);
+	if (aggref->aggorder != NIL)
+	{
+		appendStringInfoString(buf, " ORDER BY ");
+		get_rule_orderby(aggref->aggorder, aggref->args, false, context);
+	}
 	appendStringInfoChar(buf, ')');
 }