From: Josh Berkus <josh@agliodbs.com>
To: Vincent-Olivier Arsenault <vincent@up4c.com>
To: pgsql-sql@postgresql.org
Subject: Re: order by x DESC, y ASC indexing problem
Date: Thu, 03 Oct 2002 19:30:59 -0700
Message-ID: <web-1771021@davinci.ethosmedia.com> (raw)
In-Reply-To: <3D9CF7EC.8080102@up4c.com>
Vincent,
> SELECT * FROM TABLE1 ORDER BY X DESC, Y ASC;
>
> (X is a date and Y a varchar)
>
> What would that index be?
>
> Is there a function I can use, to invert x (the date), so that I can
> make a query / index set like :
PostgreSQL's sorting mechanism can use an index either ascending or
descending; it does not make a difference.
However, most of the time ORDER BY does not use an index at all because
a seq scan is faster. Usually, ORDER BY uses an index only when
combined with related criteria and/or the LIMIT clause.
-Josh Berkus
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To: pgsql-sql@postgresql.org
Cc: josh@agliodbs.com, vincent@up4c.com
Subject: Re: order by x DESC, y ASC indexing problem
In-Reply-To: <web-1771021@davinci.ethosmedia.com>
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