From: Jeff Boes <jboes@qtm.net>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040616
MIME-Version: 1.0
Subject: Inherited tables and new fields
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Lines: 44
Message-ID: <D5aLc.46510$5Y.46338@cyclops.nntpserver.com>
Date: Tue, 20 Jul 2004 10:36:02 -0400
To: pgsql-sql@postgresql.org

This feels like a flaw in the way inherited tables work.

I have a "template" table used to create other tables (but not by
inheritance; instead the "daughter" tables are created via

   create table draft_00123 as select * from draft_template where false;

This is done for somewhat historical reasons, because we weren't sure at
the time if we were going to stay with Pg and so we didn't use every
Pg-specific feature in the books.

Of course, we regret that ...

Now we have a function that spans all the daughter tables. That is, you
can do

   select * from fn_all_drafts() ...

and get rows from each table.

Of course, had we used table inheritance, we'd do something like ...

   select * from draft_template ...

but it wouldn't do exactly what we are doing now: that is,
fn_all_drafts() returns not only the contents of every row in the tables
draft_XXXXX, but also an extra column indicating which table that row
came from.

   create table all_drafts (editor_id integer) inherits draft_template;

What frustrates me from time to time is that if "draft_template" is
altered to add a new column, then the function breaks because the new
column appears in "all_drafts" as *following* editor_id. The column
order messes up the code in the function, because it's expecting
all_drafts to look like draft_template, with editor_id added at the end.

Is this a mis-feature?

-- 
(Posted from an account used as a SPAM dump. If you really want to get
in touch with me, dump the 'jboes' and substitute 'mur'.)
________
Jeffery Boes <>< jboes@qtm.net