From 7fbf0af22be6278c2b4e8c6c8c3e914b64cf9117 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 4 Apr 2000 02:30:52 +0000
Subject: [PATCH] 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 | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index ec22f1e6dd..7e76498f86 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/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;
 }