
> That explains it ...
> 
>  profiles_faith | count
> ----------------+--------
>               0 | 485938
>               1 |      2
>               2 |      6
>               7 |      2
>               8 |     21
> (5 rows)
> 
> Cool, another waste of space *sigh*
> 
> thanks ...
> 
> 
> On Wed, 13 Feb 2002, Tom Lane wrote:
> 
> > "Marc G. Fournier" <scrappy@hub.org> writes:
> > > Okay, if I'm understanding pg_stats at all, which I may not be, n_distinct
> > > should represent # of distinct values in that row, no?
> > > But, I have one field that has 5 distinct values:
> > > But pg_stats is reporting 1:
> >
> > The pg_stats values are only, um, statistical.  If 99.9% of the table is
> > the same value and the other four values appear only once or twice, it's
> > certainly possible for ANALYZE's sample to include only the common value
> > and miss the rare ones.  AFAIK that will not break anything; if you have
> > an example where the planner seems to be fooled because of this, let's
> > see it.

Hmm ? How about select * from xxx where profiles_faith = 7
would estimate all rows, no ? Instead of 2.
That is why I think a bin for "very uncommon" values could also be 
useful sometimes.

Andreas

Fri, 15 Feb 2002 18:18:35 +0100
"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>
Re: "Bug" in statistics for v7.2? 
"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at> writes:
> The pg_stats values are only, um, statistical.  If 99.9% of the table is
> the same value and the other four values appear only once or twice, it's
> certainly possible for ANALYZE's sample to include only the common value
> and miss the rare ones.  AFAIK that will not break anything; if you have
> an example where the planner seems to be fooled because of this, let's
> see it.

> Hmm ? How about select * from xxx where profiles_faith = 7
> would estimate all rows, no ? Instead of 2.

Not in 7.2 ... nor in previous versions AFAIR.

> That is why I think a bin for "very uncommon" values could also be 
> useful sometimes.

Perhaps you should experiment or read the code before opining...

			regards, tom lane

Fri, 15 Feb 2002 12:45:39 -0500
Tom Lane <tgl@sss.pgh.pa.us>
Re: "Bug" in statistics for v7.2? 