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Re: Not HOT enough

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Not HOT enough
Date: 2011-11-23 15:28:38
Message-ID: CA+TgmoYH4mZhCamFW0PjXJFLNtDtQZPhBq022qgOY=4Z9HhYaA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Nov 23, 2011 at 10:20 AM, 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?)

Hmm, I'm not seeing any increase in the number of entries in
pg_shdepend when I create either a temporary or permanent table:

rhaas=# select sum(1) from pg_shdepend;
 sum
-----
   2
(1 row)

rhaas=# create temp table xyz (a int);
CREATE TABLE
rhaas=# select sum(1) from pg_shdepend;
 sum
-----
   2
(1 row)

rhaas=# create table abc (a int);
CREATE TABLE
rhaas=# select sum(1) from pg_shdepend;
 sum
-----
   2
(1 row)

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

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Subject: Re: Not HOT enough
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