Teach eval_const_expressions to simplify BooleanTest nodes that have

constant input.  Seems worth doing because rule rewriter inserts
IS NOT TRUE tests into WHERE clauses.

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 5570b33f485d0a346c8a88d9e6788ea4a5d53102..73fe60bd24eb39eb9c3ab95d186792902d37010d 100644 (file)
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.216 2006/08/02 01:59:46 joe Exp $
+ *   $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.217 2006/08/04 14:09:51 tgl Exp $
  *
  * HISTORY
  *   AUTHOR            DATE            MAJOR EVENT
@@ -2092,6 +2092,58 @@ eval_const_expressions_mutator(Node *node,
        newfselect->resulttypmod = fselect->resulttypmod;
        return (Node *) newfselect;
    }
+   if (IsA(node, BooleanTest))
+   {
+       BooleanTest *btest = (BooleanTest *) node;
+       BooleanTest *newbtest;
+       Node       *arg;
+
+       arg = eval_const_expressions_mutator((Node *) btest->arg,
+                                            context);
+       if (arg && IsA(arg, Const))
+       {
+           Const  *carg = (Const *) arg;
+           bool    result;
+
+           switch (btest->booltesttype)
+           {
+               case IS_TRUE:
+                   result = (!carg->constisnull &&
+                             DatumGetBool(carg->constvalue));
+                   break;
+               case IS_NOT_TRUE:
+                   result = (carg->constisnull ||
+                             !DatumGetBool(carg->constvalue));
+                   break;
+               case IS_FALSE:
+                   result = (!carg->constisnull &&
+                             !DatumGetBool(carg->constvalue));
+                   break;
+               case IS_NOT_FALSE:
+                   result = (carg->constisnull ||
+                             DatumGetBool(carg->constvalue));
+                   break;
+               case IS_UNKNOWN:
+                   result = carg->constisnull;
+                   break;
+               case IS_NOT_UNKNOWN:
+                   result = !carg->constisnull;
+                   break;
+               default:
+                   elog(ERROR, "unrecognized booltesttype: %d",
+                        (int) btest->booltesttype);
+                   result = false; /* keep compiler quiet */
+                   break;
+           }
+
+           return makeBoolConst(result, false);
+       }
+
+       newbtest = makeNode(BooleanTest);
+       newbtest->arg = (Expr *) arg;
+       newbtest->booltesttype = btest->booltesttype;
+       return (Node *) newbtest;
+   }
 
    /*
     * For any node type not handled above, we recurse using