Re: Catalog Access (was: [GENERAL] Concurrency problem building indexes)

On Tue, Apr 25, 2006 at 12:25:35PM -0500, Jim C. Nasby wrote:
> Is there anything in comments/docs/list archives about why catalog
> access uses a bunch of 'magic' instead of treating catalog tables the
> same as every other table? I realize that ultimately you have to
> bootstrap somehow (kinda hard to read from pg_class if the info needed
> to do so is in pg_class), but perhaps switching over to the regular
> access methods after the system is up would be worth-while.

I don't know if it's explicitly documented, but here's one mail that
describes some of the issues:

http://www.thelinuxreview.com/pgsql-hackers/2005-03/msg00840.php

I think the basic problem is that DDL can't really work within a
transaction. If I do an ALTER TABLE, some of these changes need to show
up to concurrent transactions (maybe creating a unique index?).

I think it's like Tom says in that email, it could be done, but the
cost/benefit ratio isn't very good...

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.