From: Tom Lane <tgl@sss.pgh.pa.us>
To: Travis Whitton <tinymountain@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Grabbing Newest Records From Duplicates
Date: Fri, 16 Mar 2007 12:17:41 -0400
Message-ID: <7757.1174061861@sss.pgh.pa.us> (raw)
In-Reply-To: <cf9b4f3e0703160855q537eafe6yf3c3bbea090e5b6e@mail.gmail.com>
References: <cf9b4f3e0703160828s2cc0b9v6c01db6e8634e37e@mail.gmail.com>
<7240.1174059340@sss.pgh.pa.us>
<cf9b4f3e0703160855q537eafe6yf3c3bbea090e5b6e@mail.gmail.com>
"Travis Whitton" <tinymountain@gmail.com> writes:
> One last question, using the "weather report" example, is it going to
> improve performance for the DISTINCT ON query to add an index to the
> location and time columns?
A two-column index matching the ORDER BY that you use might help,
or then again might not --- for full-table scans it's often faster
to sort than to try to use an index.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, tinymountain@gmail.com
Subject: Re: Grabbing Newest Records From Duplicates
In-Reply-To: <7757.1174061861@sss.pgh.pa.us>
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