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)

1 files changed, 49 insertions, 1 deletions

diff --git a/src/backend/commands/creatinh.c b/src/backend/commands/creatinh.c
index 0b2d2360b3c..9463d55a6a1 100644
--- a/src/backend/commands/creatinh.c
+++ b/src/backend/commands/creatinh.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/creatinh.c,v 1.48 1999/10/03 23:55:27 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/creatinh.c,v 1.49 1999/10/15 01:49:39 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,10 +16,12 @@
 
 #include "access/heapam.h"
 #include "catalog/catname.h"
+#include "catalog/indexing.h"
 #include "catalog/heap.h"
 #include "catalog/pg_inherits.h"
 #include "catalog/pg_ipl.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_description.h"
 #include "commands/creatinh.h"
 #include "utils/syscache.h"
 
@@ -232,6 +234,52 @@ TruncateRelation(char *name)
 	heap_truncate(name);
 }
 
+/*------------------------------------------------------------------
+ * CommentRelation --
+ *                Adds a comment to pg_description for the associated
+ *                relation or relation attribute.
+ *
+ * Note:           
+ *                The comment is dropped on the relation or attribute if
+ *                the comment is an empty string.
+ *------------------------------------------------------------------
+ */
+void 
+CommentRelation(char *relname, char *attrname, char *comments) 
+{
+
+  Relation relation;
+  HeapTuple attrtuple;
+  Oid oid;
+
+  /*** First ensure relname is valid ***/
+
+  relation = heap_openr(relname, AccessShareLock);
+  
+  /*** Now, if an attribute was specified, fetch its oid, else use relation's oid ***/
+  
+  if (attrname != NULL) {
+    attrtuple = SearchSysCacheTuple(ATTNAME, ObjectIdGetDatum(relation->rd_id),
+				    PointerGetDatum(attrname), 0, 0);
+    if (!HeapTupleIsValid(attrtuple)) {
+      elog(ERROR, "CommentRelation: attribute \"%s\" is not an attribute of relation \"%s\"",
+	   attrname, relname);
+    }
+    oid = attrtuple->t_data->t_oid;
+  } else {
+    oid = RelationGetRelid(relation);
+  }
+  
+  /*** Call CreateComments() to create/drop the comments ***/
+
+  CreateComments(oid, comments);
+
+  /*** Now, close the heap relation ***/
+
+  heap_close(relation, AccessShareLock); 
+
+}
+
 /*
  * MergeAttributes
  *		Returns new schema given initial schema and supers.