| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Martijn van Oosterhout <kleptog(at)svana(dot)org> |
| Subject: | Re: Maximum statistics target |
| Date: | 2008-03-10 12:46:34 |
| Message-ID: | 12262.1205153194@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Am Freitag, 7. Mrz 2008 schrieb Tom Lane:
>> IIRC, egjoinsel is one of the weak spots, so tests involving planning of
>> joins between two tables with large MCV lists would be a good place to
>> start.
> I have run tests with joining two and three tables with 10 million rows each,
> and the planning times seem to be virtually unaffected by the statistics
> target, for values between 10 and 800000.
It's not possible to believe that you'd not notice O(N^2) behavior for N
approaching 800000 ;-). Perhaps your join columns were unique keys, and
thus didn't have any most-common-values?
regards, tom lane
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