Remove the hack in the grammar that "optimized away" DEFAULT NULL clauses.

Instead put in a test to drop a NULL default at the last moment before
storing the catalog entry.  This changes the behavior in a couple of ways:
* Specifying DEFAULT NULL when creating an inheritance child table will
  successfully suppress inheritance of any default expression from the
  parent's column, where formerly it failed to do so.
* Specifying DEFAULT NULL for a column of a domain type will correctly
  override any default belonging to the domain; likewise for a sub-domain.
The latter change happens because by the time the clause is checked,
it won't be a simple null Const but a CoerceToDomain expression.

Personally I think this should be back-patched, but there doesn't seem to
be consensus for that on pgsql-hackers, so refraining.

1 files changed, 16 insertions, 1 deletions

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 754e18d687c..86fddc4a7a6 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.221 2007/06/23 22:12:51 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.222 2007/10/29 19:40:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -606,6 +606,21 @@ transformParamRef(ParseState *pstate, ParamRef *pref)
 	return (Node *) param;
 }
 
+/* Test whether an a_expr is a plain NULL constant or not */
+static bool
+exprIsNullConstant(Node *arg)
+{
+	if (arg && IsA(arg, A_Const))
+	{
+		A_Const *con = (A_Const *) arg;
+
+		if (con->val.type == T_Null &&
+			con->typename == NULL)
+			return true;
+	}
+	return false;
+}
+
 static Node *
 transformAExprOp(ParseState *pstate, A_Expr *a)
 {