Re: Bad Planner Statistics for Uneven distribution.

"Kevin McArthur" <Kevin(at)StormTide(dot)ca> writes:
> -> Seq Scan on models_brands (cost=0.00..6411.89 rows=369489 width=4) (actual time=0.040..1352.997 rows=369489 loops=1)
> ...
> -> Index Scan using models_brands_brand on models_brands (cost=0.00..862236.96 rows=369489 width=4) (actual time=0.122..1440.809 rows=369489 loops=1)

> Picks the wrong plan here. Should pick the index with seqscanning enabled.

It's really not possible for a full-table indexscan to be faster than a
seqscan, and not very credible for it even to be approximately as fast.
I suspect your second query here is the beneficiary of the first query
having fetched all the pages into cache. In general, if you want to
optimize for a mostly-cached database, you need to reduce
random_page_cost below its default value ...

regards, tom lane