Break transformCreateStmt() into multiple routines and make

transformAlterStmt() use these routines, instead of having lots of
duplicate (not to mention should-have-been-duplicate) code.
Adding a column with a CHECK constraint actually works now,
and the tests to reject unsupported DEFAULT and NOT NULL clauses
actually fire now.  ALTER TABLE ADD PRIMARY KEY works, modulo
having to have created the column(s) NOT NULL already.

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parsenodes.h,v 1.145 2001/10/02 21:39:36 tgl Exp $
+ * $Id: parsenodes.h,v 1.146 2001/10/12 00:07:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -187,6 +187,12 @@ typedef struct CopyStmt
 
 /* ----------------------
  *		Create Table Statement
+ *
+ * NOTE: in the raw gram.y output, ColumnDef, Constraint, and FkConstraint
+ * nodes are intermixed in tableElts, and constraints is NIL.  After parse
+ * analysis, tableElts contains just ColumnDefs, and constraints contains
+ * just Constraint nodes (in fact, only CONSTR_CHECK nodes, in the present
+ * implementation).
  * ----------------------
  */
 typedef struct CreateStmt
@@ -196,8 +202,7 @@ typedef struct CreateStmt
 	List	   *tableElts;		/* column definitions (list of ColumnDef) */
 	List	   *inhRelnames;	/* relations to inherit from (list of
 								 * T_String Values) */
-	List	   *constraints;	/* constraints (list of Constraint and
-								 * FkConstraint nodes) */
+	List	   *constraints;	/* constraints (list of Constraint nodes) */
 	bool		istemp;			/* is this a temp table? */
 	bool		hasoids;		/* should it have OIDs? */
 } CreateStmt;