From: Joshua D. Drake <jd@commandprompt.com>
To: gabriel.biberian@beemotechnologie.com
Cc: pgsql-performance@postgresql.org
Subject: Re: slow update on 1M rows (worse with indexes)
Date: Thu, 22 Feb 2007 10:42:39 -0800
Message-ID: <45DDE41F.6090907@commandprompt.com> (raw)
In-Reply-To: <45DDDCDE.9050806@beemotechnologie.com>
References: <45DDDCDE.9050806@beemotechnologie.com>
n i tried adding an index to the table on the column date (int) that
> stores unix timestamps.
> TOTO=# CREATE INDEX versions_index ON versions_9d (date);
> (-60M) disk space goes down on index creation
> beebox@evobrik01:~$ time psql TOTO -c "UPDATE versions_9d SET flag=9"
> UPDATE 976009
> real 3m8.219s (+328M)
> beebox@evobrik01:~$ time psql TOTO -c "UPDATE versions_9d SET flag=8"
> UPDATE 976009
> real 6m24.716s (+326M)
> beebox@evobrik01:~$ time psql TOTO -c "UPDATE versions_9d SET flag=10"
> UPDATE 976009
> real 8m25.274s (+321M)
>
> As a sanity check, i loaded mysql5 and tried the same database and
> updates. With mysql, the update always lasts ~8s.
Yes but with mysql did you use myisam or innodb?
> The conclusions I have come to is that update==insert+delete which seems
> very heavy when index are present (and heavy disk wise on big tables).
> Is there a switch i can flip to optimise this?
>
> Thanks in advance,
> Gabriel Biberian
>
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To: pgsql-performance@postgresql.org
Cc: jd@commandprompt.com, gabriel.biberian@beemotechnologie.com
Subject: Re: slow update on 1M rows (worse with indexes)
In-Reply-To: <45DDE41F.6090907@commandprompt.com>
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