Re: ANALYZE estimates very wrong reltuples

Thanks for the pointer! I think I need to read some docs about the planner
statistics.

I tried 1000 and the result was 36M, closer but not enough.

Then tried 10000, it tool half an hour to scan all the pages and got the
accurate number.

Thanks again!

On Wed, Feb 20, 2013 at 6:50 PM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>wrote:

> Qingbo Zhou wrote:
> > I have a table which has ~26M records in it. But pg_class shows ~35M in
> the "reltuples" column.
> > last_autovacuum is null, and last_autoanalyze was just on yesterday.
> >
> > I tried running vacuum analyze on it, but the analyze result shows:
> >
> > INFO: "[table name]": scanned 30000 of 950145 pages, containing 805842
> live rows and 11109 dead rows;
> > 30000 rows in sample, 42266462 estimated total rows
> >
> >
> > Even worse estimates. I know that it's doing an estimate, but it's too
> wrong. I have another table for
> > which pg_class estimates 3 times the actual number of rows.
> >
> > I'm using 9.1.3 [...]
>
> Could you try with different settings for default_statistics_target
> (1000, 10000) and see if that changes the result of
> ANALYZE VERBOSE?
>
> Yours,
> Laurenz Albe
>