Re: Need help in setting optimal configuration for a huge

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Craig A(dot) James" <cjames(at)modgraph-usa(dot)com>
Cc: Kishore B <kishorebh(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Need help in setting optimal configuration for a huge
Date: 2005-10-23 17:06:07
Message-ID: 20903.1130087167@sss.pgh.pa.us
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"Craig A. James" <cjames(at)modgraph-usa(dot)com> writes:
> MIN() and MAX() -- These are surprisingly slow, because they seem to do a full table scan EVEN ON AN INDEXED COLUMN! I don't understand why, but happily there is an effective substitute:

> select mycolumn from mytable order by mycolumn limit 1; -- same as MIN()

> select mycolumn from mytable order by mycolumn desc limit 1; -- same as MAX()

BTW, Postgres does know to do that for itself as of 8.1.

regards, tom lane

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