Re: unlogged tables

On Mon, Nov 15, 2010 at 10:54 AM, Marti Raudsepp <marti@juffo.org> wrote:
> On Sun, Nov 14, 2010 at 02:16, Robert Haas <robertmhaas@gmail.com> wrote:
>> Here is a series of three patches related to unlogged tables.
>
> Just wondering, have you thought of any mechanisms how application
> code might detect that an unlogged table was truncated due to restart?
> While polling with something like "SELECT 1 FROM table LIMIT 1" might
> work, it's an awful hack.
>
> One obvious use case for these unlogged tables would be materalized
> views. I think it would be useful to execute e.g. a TRUNCATE trigger
> so that an the view could be initialized. If an exclusive lock were
> passed on to the trigger procedure, this could even be done in a
> race-condition-free manner as far as I can tell.
>
> Would there be a problem with invoking this trigger from the session
> that first touches the table?

Yeah, this infrastructure doesn't really allow that.  The truncate
happens way too early on in startup to execute any user-provided code.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company