| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
| Cc: | Maksim Likharev <mlikharev(at)aurigin(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Statistics on a table |
| Date: | 2003-07-09 06:32:49 |
| Message-ID: | 28754.1057732369@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> writes:
>> statistic ( n_distinct in particular) records for one of my columns,
>> greatly under calculated it saying:
>> 49726, but in reality 33409816.
>> is it any way how I can improve that?
> You might see if raising the statistics target with ALTER TABLE ALTER
> COLUMN followed by an analyze helps getting reasonable values any. Maybe
> try a few thousand?
That seems like a big jump, considering the default is only 10. Try
setting it to 100 (then re-ANALYZE, then check the plan). If that
doesn't work, try more. I'd be interested to see what it takes to
get the estimate closer to reality.
regards, tom lane
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