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Re: Not HOT enough

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Alvaro Herrera <alvherre(at)commandprompt(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 16:14:04
Message-ID: CA+U5nM+RBxcgmEWgp8znjK0QYCyaTsLdRZWdJkVtg8--6H-NKw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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.

If catalogs need VACUUMing then autovacuum takes care of it.

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

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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