This patch implements ORACLE's COMMENT SQL command.

>From the ORACLE 7 SQL Language Reference Manual:
-----------------------------------------------------
COMMENT

Purpose:

To add a comment about a table, view, snapshot, or
column into the data dictionary.

Prerequisites:

The table, view, or snapshot must be in your own
schema
or you must have COMMENT ANY TABLE system privilege.

Syntax:

COMMENT ON [ TABLE table ] |
           [ COLUMN table.column] IS 'text'

You can effectively drop a comment from the database
by setting it to the empty string ''.
-----------------------------------------------------

Example:

COMMENT ON TABLE workorders IS
   'Maintains base records for workorder information';

COMMENT ON COLUMN workorders.hours IS
   'Number of hours the engineer worked on the task';

to drop a comment:

COMMENT ON COLUMN workorders.hours IS '';

The current patch will simply perform the insert into
pg_description, as per the TODO. And, of course, when
the table is dropped, any comments relating to it
or any of its attributes are also dropped. I haven't
looked at the ODBC source yet, but I do know from
an ODBC client standpoint that the standard does
support the notion of table and column comments.
Hopefully the ODBC driver is already fetching these
values from pg_description, but if not, it should be
trivial.

Hope this makes the grade,

Mike Mascari
(mascarim@yahoo.com)

src/include/nodes/parsenodes.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parsenodes.h,v 1.84 1999/10/07 04:23:17 tgl Exp $
+ * $Id: parsenodes.h,v 1.85 1999/10/15 01:49:47 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -309,6 +309,18 @@ typedef struct TruncateStmt
         NodeTag         type;
         char	   *relName;            /* relation to be truncated */
 } TruncateStmt;
+
+/* ----------------------
+ *              Comment On Statement
+ * ----------------------
+ */
+typedef struct CommentStmt
+{
+  NodeTag         type;
+  char *relname;                       /* relation to create/drop comment */
+  char *attrname;                      /* attribute to comment on */
+  char *comment;                       /* the actual comment */
+} CommentStmt;
       
 /* ----------------------
  *		Extend Index Statement