When rewriting an aggregate introduced into WHERE, allow agg argument to

be an expression not just a simple Var, so long as only one table is
referenced (so that code isn't really any more difficult than before).
This whole thing is still fundamentally bogus, but at least we can accept
a few more cases than before.

src/backend/rewrite/rewriteHandler.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.69 2000/03/16 03:23:18 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.70 2000/04/04 02:30:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,6 +20,7 @@
 #include "nodes/makefuncs.h"
 #include "optimizer/clauses.h"
 #include "optimizer/prep.h"
+#include "optimizer/var.h"
 #include "parser/analyze.h"
 #include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
@@ -437,8 +438,8 @@ modifyAggrefDropQual(Node *node, Node *targetNode)
 static SubLink *
 modifyAggrefMakeSublink(Aggref *aggref, Query *parsetree)
 {
-	/* target and rte point to old structures: */
-	Var		   *target;
+	List	   *aggVarNos;
+	/* rte points to old structure: */
 	RangeTblEntry *rte;
 	/* these point to newly-created structures: */
 	Query	   *subquery;
@@ -446,10 +447,10 @@ modifyAggrefMakeSublink(Aggref *aggref, Query *parsetree)
 	TargetEntry *tle;
 	Resdom	   *resdom;
 
-	target = (Var *) (aggref->target);
-	if (! IsA(target, Var))
-		elog(ERROR, "rewrite: aggregates of views only allowed on simple variables for now");
-	rte = rt_fetch(target->varno, parsetree->rtable);
+	aggVarNos = pull_varnos(aggref->target);
+	if (length(aggVarNos) != 1)
+		elog(ERROR, "rewrite: aggregates of views only allowed on single tables for now");
+	rte = rt_fetch(lfirsti(aggVarNos), parsetree->rtable);
 
 	resdom = makeNode(Resdom);
 	resdom->resno = 1;
@@ -503,11 +504,13 @@ modifyAggrefMakeSublink(Aggref *aggref, Query *parsetree)
 	/* Increment all varlevelsup fields in the new subquery */
 	IncrementVarSublevelsUp((Node *) subquery, 1, 0);
 
-	/* Replace references to the target table with correct local varno.
-	 * Note +1 here to account for effects of previous line!
+	/* Replace references to the target table with correct local varno, 1.
+	 * Note that because of previous line, these references have
+	 * varlevelsup = 1, which must be changed to 0.
 	 */
-	modifyAggrefChangeVarnodes((Node *) subquery, target->varno,
-							   1, target->varlevelsup+1, 0);
+	modifyAggrefChangeVarnodes((Node *) subquery,
+							   lfirsti(aggVarNos), 1,
+							   1, 0);
 
 	return sublink;
 }