Add a paramtypmod field to Param nodes. This is dead weight for Params

representing externally-supplied values, since the APIs that carry such
values only specify type not typmod.  However, for PARAM_SUBLINK Params
it is handy to carry the typmod of the sublink's output column.  This
is a much cleaner solution for the recently reported 'could not find
pathkey item to sort' and 'failed to find unique expression in subplan
tlist' bugs than my original 8.2-compatible patch.  Besides, someday we
might want to support typmods for external parameters ...

src/backend/parser/parse_coerce.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.146 2006/11/28 12:54:41 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.147 2006/12/10 22:13:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -264,6 +264,14 @@ coerce_type(ParseState *pstate, Node *node,
 		}
 
 		param->paramtype = targetTypeId;
+		/*
+		 * Note: it is tempting here to set the Param's paramtypmod to
+		 * targetTypeMod, but that is probably unwise because we have no
+		 * infrastructure that enforces that the value delivered for a
+		 * Param will match any particular typmod.  Leaving it -1 ensures
+		 * that a run-time length check/coercion will occur if needed.
+		 */
+		param->paramtypmod = -1;
 
 		return (Node *) param;
 	}