From 507b53c8338c176edb27804573e5747874b171f2 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 24 Jul 2007 17:22:07 +0000
Subject: [PATCH] Fix predicate-proving logic to cope with binary-compatibility
cases when checking whether an IS NULL/IS NOT NULL clause is implied or
refuted by a strict function. Per example from Dawid Kuroczko. Backpatch to
8.2 since this is arguably a performance bug.
---
src/backend/optimizer/util/predtest.c | 41 +++++++++++++++++++++++----
1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/src/backend/optimizer/util/predtest.c b/src/backend/optimizer/util/predtest.c
index 9bdef7a319c..3280612dfd5 100644
--- a/src/backend/optimizer/util/predtest.c
+++ b/src/backend/optimizer/util/predtest.c
@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/util/predtest.c,v 1.15 2007/05/12 19:22:35 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/util/predtest.c,v 1.16 2007/07/24 17:22:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -84,6 +84,7 @@ static bool predicate_implied_by_simple_clause(Expr *predicate, Node *clause);
static bool predicate_refuted_by_simple_clause(Expr *predicate, Node *clause);
static bool is_null_contradicts(NullTest *ntest, Node *clause);
static Node *extract_not_arg(Node *clause);
+static bool list_member_strip(List *list, Expr *datum);
static bool btree_predicate_proof(Expr *predicate, Node *clause,
bool refute_it);
@@ -961,11 +962,11 @@ predicate_implied_by_simple_clause(Expr *predicate, Node *clause)
if (!type_is_rowtype(exprType((Node *) nonnullarg)))
{
if (is_opclause(clause) &&
- list_member(((OpExpr *) clause)->args, nonnullarg) &&
+ list_member_strip(((OpExpr *) clause)->args, nonnullarg) &&
op_strict(((OpExpr *) clause)->opno))
return true;
if (is_funcclause(clause) &&
- list_member(((FuncExpr *) clause)->args, nonnullarg) &&
+ list_member_strip(((FuncExpr *) clause)->args, nonnullarg) &&
func_strict(((FuncExpr *) clause)->funcid))
return true;
}
@@ -1044,11 +1045,11 @@ is_null_contradicts(NullTest *ntest, Node *clause)
/* foo IS NULL contradicts any strict op/func on foo */
if (is_opclause(clause) &&
- list_member(((OpExpr *) clause)->args, isnullarg) &&
+ list_member_strip(((OpExpr *) clause)->args, isnullarg) &&
op_strict(((OpExpr *) clause)->opno))
return true;
if (is_funcclause(clause) &&
- list_member(((FuncExpr *) clause)->args, isnullarg) &&
+ list_member_strip(((FuncExpr *) clause)->args, isnullarg) &&
func_strict(((FuncExpr *) clause)->funcid))
return true;
@@ -1091,6 +1092,36 @@ extract_not_arg(Node *clause)
}
+/*
+ * Check whether an Expr is equal() to any member of a list, ignoring
+ * any top-level RelabelType nodes. This is legitimate for the purposes
+ * we use it for (matching IS [NOT] NULL arguments to arguments of strict
+ * functions) because RelabelType doesn't change null-ness. It's helpful
+ * for cases such as a varchar argument of a strict function on text.
+ */
+static bool
+list_member_strip(List *list, Expr *datum)
+{
+ ListCell *cell;
+
+ if (datum && IsA(datum, RelabelType))
+ datum = ((RelabelType *) datum)->arg;
+
+ foreach(cell, list)
+ {
+ Expr *elem = (Expr *) lfirst(cell);
+
+ if (elem && IsA(elem, RelabelType))
+ elem = ((RelabelType *) elem)->arg;
+
+ if (equal(elem, datum))
+ return true;
+ }
+
+ return false;
+}
+
+
/*
* Define an "operator implication table" for btree operators ("strategies"),
* and a similar table for refutation.
--
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