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Re: multicolumn index column order

From: valgog <valgog(at)gmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: multicolumn index column order
Date: 2007-07-25 08:34:00
Message-ID: 1185352440.504985.282370@19g2000hsx.googlegroups.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Jul 25, 2:14 am, Lew <l(dot)(dot)(dot)(at)lewscanon(dot)nospam> wrote:
>
> How about two indexes, one on each column?  Then the indexes will cooperate
> when combined in a WHERE clause.
> <http://www.postgresql.org/docs/8.2/interactive/indexes-bitmap-scans.html>
>
> I don't believe the index makes a semantic difference with regard to ascending
> or descending.  An index is used to locate records in the selection phase of a
> query or modification command.
>
> --
> Lew

Ordered indexes (b-tree in this case) are also used to get the needed
record order and it is absolutely not necessary to have a WHARE clause
in your select statement to use them when you are using ORDER BY.

--
Valentine


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