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Re: Not HOT enough

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Not HOT enough
Date: 2011-11-23 17:00:55
Message-ID: 1322067518-sup-5258@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Excerpts from Simon Riggs's message of mié nov 23 13:14:04 -0300 2011:
> On Wed, Nov 23, 2011 at 3:20 PM, Alvaro Herrera
> <alvherre(at)commandprompt(dot)com> wrote:
> >
> > Excerpts from Robert Haas's message of mié nov 23 12:15:55 -0300 2011:
> >
> >> > And it effects shared catalogs only, which are all low traffic anyway.
> >>
> >> I think "low traffic" is the key point.  I understand that you're not
> >> changing the VACUUM behavior, but you are making heap_page_prune_opt()
> >> not do anything when a shared catalog is involved.  That would be
> >> unacceptable if we expected shared catalogs to be updated frequently,
> >> either now or in the future, but I guess we don't expect that.
> >
> > Maybe not pg_database or pg_tablespace and such, but I'm not so sure
> > about pg_shdepend.  (Do we record pg_shdepend entries for temp tables?)
> 
> Normal catalog access does not use HOT and never has.

Oh.

> If we're saying that isn't enough and we actually depend on the
> occasional user inspecting the catalog then we are already hosed.

Probably not.  I have heard of cases of pg_shdepend getting bloated
though, so it'd be nice if it happened.

-- 
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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