From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Reinoud van Leeuwen <reinoud(at)xs4all(dot)nl>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: optimizer question |
Date: | 2001-10-11 21:17:04 |
Message-ID: | 200110112117.f9BLH4N14100@candle.pha.pa.us |
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Lists: | pgsql-hackers |
> "Reinoud van Leeuwen" <reinoud(at)xs4all(dot)nl> writes:
> > I have a table that contains almost 8 milion rows. The primary key is a
> > sequence, so the index should have a good distribution. Why does the
> > optimizer refuse to use the index for getting the maximum value?
>
> The optimizer has no idea that max() has anything to do with indexes.
> You could try something like
>
> select * from tab order by foo desc limit 1;
Can we consider doing this optimization automatically?
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
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