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Re: SELECT * FROM <table> LIMIT 1; is really slow

From: Manfred Koizar <mkoi-pg(at)aon(dot)at>
To: Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,David Blasby <dblasby(at)refractions(dot)net>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: SELECT * FROM <table> LIMIT 1; is really slow
Date: 2004-05-28 18:29:51
Message-ID: 8f0fb0drfn3rl4hj6ercgf98021894444i@email.aon.at (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, 27 May 2004 16:50:24 -0400, Alvaro Herrera
<alvherre(at)dcc(dot)uchile(dot)cl> wrote:
>Now you are on the subject, can I ask you to take a peek at what I did
>regarding tuple headers?

I did read your patch, but I didn't understand it. :-(

>At first I thought I'd have to add back Xmax as a field on its own

Veto!  This would increase heap tuple header size ==> less tuples per
page ==> more pages per table ==> more I/O ==> performance loss.

> is there a situation
>on which we should need to peek at Cmin after setting Xmax for a
>particusar tuple?

http://archives.postgresql.org/pgsql-hackers/2002-05/msg00090.php


Servus
 Manfred

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Next:From: Tom LaneDate: 2004-05-28 18:47:01
Subject: Re: SELECT * FROM <table> LIMIT 1; is really slow
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Subject: pg_autovacuum Integration

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