Re: Query optimizer 8.0.1 (and 8.0)

Josh Berkus wrote:
> Mark, Stephen, etc:
>
> > > I can see your point, however I wonder if the issue is that the default
> > > stats settings of '10' (3000 rows, 10 histogram buckets) is too low, and
> > > maybe we should consider making a higher value (say '100') the default.
> >
> > Personally, I think that'd be reasonable.
>
> I don't really think that we want to increase sampling for *all* columns.
> Each column that doesn't get queried but has increased stats adds the size of
> the pg_stats table and the amount of vacuuming it needs, decreasing
> performance of stats lookups. Especially when very large text and BYTEA
> columns are involved.
>
> Neil and I talked about setting a seperate GUC, default_index_stats_target,
> for 8.0 that would dramatically increase the stats sampling for indexed
> columns only (say, to 250). Unfortunately, I was unable to come up with a
> good test case for setting this value.

Is default_index_stats_target a TODO item? Seems we already have cases
where our bucket size isn't large enough and this would help.

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