Re: How reliable are the stats collector stats?

On Mar 13, 2004, at 12:51 AM, Tom Lane wrote:

> Eric Ridge <ebr@tcdi.com> writes:
>> Could pg_stats_user_indexes be lying?
>
> Jan probably knows this stuff better than I, but my guess is that if
> the
> counter type you are looking at is incrementing at all, then it's not
> too far off.

Many of the indexes that report zero usage I agree with.  Only a few
seem questionable.  Double-checking the queries (and their plans) will
provide the only true answer.

> I certainly can't think of a failure mechanism that would
> cause some indexes to be shown with zero hits when other indexes do
> get hits.

This is good to know.  I don't have specifics handy, but I've seen a
few columns from the pg_statio_user_tables view come back w/ null
values.  Oh yeah, this is against v7.3.4.

>> I realize the real question is "why aren't these indexes being used",
>
> Up to a point.  If it's a unique index then you may want the
> uniqueness-check functionality even if the index is never used for
> searches.

Very good point.  Fortunately the indexes in question are not unique
indexes.

thanks!

eric