Re: Why we don't want hints

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От Scott Marlowe
Тема Re: Why we don't want hints
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Msg-id AANLkTik8hhy9UOAMgQnM-=fi0eZ0x=0=o=b=_N=qJxHY@mail.gmail.com
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Ответ на Re: [HACKERS] Slow count(*) again...  (Mladen Gogala <mladen.gogala@vmsinfo.com>)
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On Sun, Feb 13, 2011 at 10:49 PM, Josh Berkus <josh@agliodbs.com> wrote:
>
>> I fail to see how 1 through 3 can tell the planner the correlation
>> between two fields in two separate tables.
>
> CREATE CORRELATION_ESTIMATE ( table1.colA ) = ( table2.colB ) IS 0.3
>
> ... and then it fixes the correlation for *every* query in the database, not
> just that one.  And is easy to fix if the correlation changes.

I like that.  Even better, could we setup some kind of simple command
to tell analyze to collect stats for the two columns together?

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