Re: postgresql meltdown on PlanetMath.org

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От Neil Conway
Тема Re: postgresql meltdown on PlanetMath.org
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Msg-id 33137.130.15.224.150.1047881939.squirrel@mailbox.samurai.com
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Ответ на Re: postgresql meltdown on PlanetMath.org  (Sean Chittenden <sean@chittenden.org>)
Ответы Re: postgresql meltdown on PlanetMath.org  (Sean Chittenden <sean@chittenden.org>)
Re: postgresql meltdown on PlanetMath.org  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-performance
Sean Chittenden said:
>> A "select count(*) FROM tblwordidx" initially took about 1 second to
>> return a count of 2 million but after a few months it took several
>> minutes of really hard HDD grinding.
>
> That's because there are dead entries in the index that weren't being
> reused or cleaned up.  As I said, this has been fixed.

That's doubtful: "select count(*) FROM foo" won't use an index. There are
a bunch of other factors (e.g. dead heap tuples, changes in the pages
cached in the buffer, disk fragmentation, etc.) that could effect
performance in that situation, however.

Cheers,

Neil



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