Re: Are statistics gathered on function indexes?

Tom,

> Ray Ontko <rayo(at)ontko(dot)com> writes:
> > 1) here's the "bad" stats.
> > 2) here's the "good" stats.
> > Note that the information really is different.
>
> Yeah. It seems that the critical difference is the null_frac; if I take
> your "bad" values and change null_frac to 0 then I get
> reasonable-looking answers, but with null_frac = 0.000333333 I indeed
> get bad answers. I suspect null_frac is getting double-counted
> somewhere, and depending on just how many nulls ANALYZE happens to find,
> you might get pushed over the edge from a small selectivity to zero or
> negative selectivity. Will dig further.

Does this help?

develop=# select count(*) from actor where actor_full_name is not null ;
count
--------
433809
(1 row)

develop=# select count(*) from actor ;
count
--------
433902
(1 row)

Ray
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