| From: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
|---|---|
| To: | Maksim Likharev <mlikharev(at)aurigin(dot)com> |
| Cc: | <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Statistics on a table |
| Date: | 2003-07-09 02:53:28 |
| Message-ID: | 20030708195151.C5781-100000@megazone23.bigpanda.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
On Tue, 8 Jul 2003, Maksim Likharev wrote:
> Hi,
> I just found very interesting situation,
> statistic ( n_distinct in particular) records for one of my columns,
> greatly under calculated it saying:
>
> 49726, but in reality 33409816.
>
> So planer never choose index but rather using table scan, and query
> never returns,
> 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?
> I can turn seqscan off but is it safe?
It's somewhat of a large hammer, especially if you're doing joins with
this table or something.
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