Re: *very* slow query to summarize data for a month ...

Neil Conway <neilc(at)samurai(dot)com> writes:
> Interesting that we get the row count estimate for this index scan so
> wrong -- I believe this is the root of the problem. Hmmm... I would
> guess that the optimizer stats we have for estimating the selectivity
> of a functional index is pretty primitive, but I haven't looked into
> it at all. Tom might be able to shed some light...

Try "none at all". I have speculated in the past that it would be worth
gathering statistics about the contents of functional indexes, but it's
still on the to-do-someday list.

>> -> Seq Scan on traffic_logs ts (cost=0.00..38340.72 rows=8213 width=16) (actual time=5.02..-645982.04 rows=462198 loops=1)

> Uh, what?

That is bizarre, all right. Is it reproducible?

regards, tom lane