From: | "Hiroshi Inoue" <Inoue(at)tpf(dot)co(dot)jp> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | <pgsql-hackers(at)postgreSQL(dot)org> |
Subject: | RE: [HACKERS] Some notes on optimizer cost estimates |
Date: | 2000-01-21 01:44:20 |
Message-ID: | 000b01bf63b1$093cbd40$2801007e@tpf.co.jp |
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Lists: | pgsql-hackers |
> -----Original Message-----
> From: owner-pgsql-hackers(at)postgreSQL(dot)org
> [mailto:owner-pgsql-hackers(at)postgreSQL(dot)org]On Behalf Of Tom Lane
>
> I have been spending some time measuring actual runtimes for various
> sequential-scan and index-scan query plans, and have learned that the
> current Postgres optimizer's cost estimation equations are not very
> close to reality at all.
>
Thanks for your good analysis.
I also have said current cost estimation for index-scan is too low.
But I have had no concrete numerical values.
I've wondered why we cound't analyze database without vacuum.
We couldn't run vacuum light-heartedly because it acquires an
exclusive lock for the target table.
In addition,vacuum error occurs with analyze option in most
cases AFAIK.
Regards.
Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp
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