Fix incorrect hash equality operator bug in Memoize

In v14, because we don't have a field in RestrictInfo to cache both the
left and right type's hash equality operator, we just restrict the scope
of Memoize to only when the left and right types of a RestrictInfo are the
same.

In master we add another field to RestrictInfo and cache both hash
equality operators.

Reported-by: Jaime Casanova
Author: David Rowley
Discussion: https://postgr.es/m/20210929185544.GB24346%40ahch-to
Backpatch-through: 14

diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index e25dc9a7ca7c25acfedbaf70d2ccb09ff48f6f68..276e62b74b6d921f87109cbc1637f86e017db771 100644 (file)
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -2719,7 +2719,8 @@ check_memoizable(RestrictInfo *restrictinfo)
 {
    TypeCacheEntry *typentry;
    Expr       *clause = restrictinfo->clause;
-   Node       *leftarg;
+   Oid         lefttype;
+   Oid         righttype;
 
    if (restrictinfo->pseudoconstant)
        return;
@@ -2728,10 +2729,20 @@ check_memoizable(RestrictInfo *restrictinfo)
    if (list_length(((OpExpr *) clause)->args) != 2)
        return;
 
-   leftarg = linitial(((OpExpr *) clause)->args);
+   lefttype = exprType(linitial(((OpExpr *) clause)->args));
+   righttype = exprType(lsecond(((OpExpr *) clause)->args));
+
+   /*
+    * Really there should be a field for both the left and right hash
+    * equality operator, however, in v14, there's only a single field in
+    * RestrictInfo to record the operator in, so we must insist that the left
+    * and right types match.
+    */
+   if (lefttype != righttype)
+       return;
 
-   typentry = lookup_type_cache(exprType(leftarg), TYPECACHE_HASH_PROC |
-                                TYPECACHE_EQ_OPR);
+   typentry = lookup_type_cache(lefttype, TYPECACHE_HASH_PROC |
+                                          TYPECACHE_EQ_OPR);
 
    if (!OidIsValid(typentry->hash_proc) || !OidIsValid(typentry->eq_opr))
        return;