Rule rewriter was doing the wrong thing with conditional INSTEAD rules

whose conditions might yield NULL.  The negated qual to attach to the
original query is properly 'x IS NOT TRUE', not 'NOT x'.  This fix
produces correct behavior, but we may be taking a performance hit because
the planner is much stupider about IS NOT TRUE than it is about NOT
clauses.  Future TODO: teach prepqual, other parts of planner how to
cope with BooleanTest clauses more effectively.

1 files changed, 12 insertions, 20 deletions

diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index 12154b8da6e..94a940648c0 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteManip.c,v 1.66 2002/09/11 14:48:54 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteManip.c,v 1.67 2002/10/20 00:58:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -690,34 +690,26 @@ AddHavingQual(Query *parsetree, Node *havingQual)
 	parsetree->hasSubLinks |= checkExprHasSubLink(copy);
 }
 
-#ifdef NOT_USED
-void
-AddNotHavingQual(Query *parsetree, Node *havingQual)
-{
-	Node	   *notqual;
-
-	if (havingQual == NULL)
-		return;
-
-	/* Need not copy input qual, because AddHavingQual will... */
-	notqual = (Node *) make_notclause((Expr *) havingQual);
-
-	AddHavingQual(parsetree, notqual);
-}
-#endif
 
+/*
+ * Invert the given clause and add it to the WHERE qualifications of the
+ * given querytree.  Inversion means "x IS NOT TRUE", not just "NOT x",
+ * else we will do the wrong thing when x evaluates to NULL.
+ */
 void
-AddNotQual(Query *parsetree, Node *qual)
+AddInvertedQual(Query *parsetree, Node *qual)
 {
-	Node	   *notqual;
+	BooleanTest *invqual;
 
 	if (qual == NULL)
 		return;
 
 	/* Need not copy input qual, because AddQual will... */
-	notqual = (Node *) make_notclause((Expr *) qual);
+	invqual = makeNode(BooleanTest);
+	invqual->arg = qual;
+	invqual->booltesttype = IS_NOT_TRUE;
 
-	AddQual(parsetree, notqual);
+	AddQual(parsetree, (Node *) invqual);
 }