Ensure that the result of evaluating a function during constant-expression

simplification gets detoasted before it is incorporated into a Const node.
Otherwise, if an immutable function were to return a TOAST pointer (an
unlikely case, but it can be made to happen), we would end up with a plan
that depends on the continued existence of the out-of-line toast datum.

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 9b8bbf87b74eef3388267c4923f030dd29571435..8d2a71c1fde063aa8290a315f55e4c10409a5492 100644 (file)
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.109.2.1 2005/04/14 21:44:46 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.109.2.2 2007/10/11 21:28:39 tgl Exp $
  *
  * HISTORY
  *       AUTHOR                        DATE                    MAJOR EVENT
@@ -1702,9 +1702,20 @@ simplify_op_or_func(Expr *expr, List *args)
        const_val = ExecEvalExprSwitchContext((Node *) newexpr, econtext,
                                                                                  &const_is_null, NULL);
 
-       /* Must copy result out of sub-context used by expression eval */
+       /*
+        * Must copy result out of sub-context used by expression eval.
+        *
+        * Also, if it's varlena, forcibly detoast it.  This protects us against
+        * storing TOAST pointers into plans that might outlive the referenced
+        * data.
+        */
        if (!const_is_null)
-               const_val = datumCopy(const_val, resultTypByVal, resultTypLen);
+       {
+               if (resultTypLen == -1)
+                       const_val = PointerGetDatum(PG_DETOAST_DATUM_COPY(const_val));
+               else
+                       const_val = datumCopy(const_val, resultTypByVal, resultTypLen);
+       }
 
        FreeExprContext(econtext);
        pfree(newexpr);