| From: | "A(dot) Kretschmer" <andreas(dot)kretschmer(at)schollglas(dot)com> |
|---|---|
| To: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Performance UPDATE/INSERT |
| Date: | 2006-04-11 10:27:57 |
| Message-ID: | 20060411102756.GF5520@webserv.wug-glas.de |
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| Lists: | pgsql-general |
am 11.04.2006, um 12:15:41 +0200 mailte Alban Hertroys folgendes:
> MG wrote:
> >I have to improve the performance of the UPDATES and I was wondering why
> >the UPDATEs need twice as long as the INSERTs.
>
> IIRC, an UPDATE is a DELETE/INSERT combo. That's because the original
> record still needs to be visible to other existing transactions (because of
> MVCC). You can't change its data but need to create a new record instead
> and mark the original as obsolete.
Correctly, and thats why we need VACUUM to clean the space on the disk.
HTH, Andreas
--
Andreas Kretschmer (Kontakt: siehe Header)
Heynitz: 035242/47215, D1: 0160/7141639
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