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 24d3b09cf13fc38285c56427a01e0db97d7c8668..c541713f3f96826053f9ce833e4906bdec2958b0 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 1.249 2007/09/06 17:31:58 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.250 2007/10/11 21:27:49 tgl Exp $
  *
  * HISTORY
  *       AUTHOR                        DATE                    MAJOR EVENT
@@ -3265,9 +3265,20 @@ evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod)
        /* Get back to outer memory context */
        MemoryContextSwitchTo(oldcontext);
 
-       /* 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);
+       }
 
        /* Release all the junk we just created */
        FreeExecutorState(estate);