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Re: avoiding seq scans when two columns are very correlated - Mailing list pgsql-performance

From Ruslan Zakirov
Subject Re: avoiding seq scans when two columns are very correlated
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Msg-id CAMOxC8stcOyn1HyCfmzwjki7EQ4edqLqNYv+v=Lt9Hq7rHeL5w@mail.gmail.com
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In response to Re: avoiding seq scans when two columns are very correlated  (Stuart Bishop <stuart@stuartbishop.net>)
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On Tue, Nov 15, 2011 at 11:08 AM, Stuart Bishop <stuart@stuartbishop.net> wrote:
> On Fri, Nov 11, 2011 at 10:01 PM, Ruslan Zakirov <ruz@bestpractical.com> wrote:
>> Hello,

[snip]

>> In application such wrong estimation result in seq scan of this table
>> winning leading position in execution plans over other tables and
>> index scans.
>>
>> What can I do to avoid this problem?
>
> Does a partial index help? CREATE UNIQUE INDEX foo_idx ON mytab(id)
> WHERE id = EffectiveId

It doesn't help. Probably reason is the same as for partitions.

>
>
> --
> Stuart Bishop <stuart@stuartbishop.net>
> http://www.stuartbishop.net/
>



--
Best regards, Ruslan.

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