Re: Sequence vs. Index Scan

On Sat, May 05, 2007 at 05:00:53PM -0500, Aaron Bono wrote:
>
> They have different data. The fast one has about 150 rows and the slow one
> has about 40 rows. The field in question here, the branch_id, is a
> BIGSERIAL in both.

I'd be astonished if a table of 40 rows ever got index scanned. It's
probably more efficient to read the whole table. But it seems your
case may be strange.

> We don't allow deletes and updates are fairly infrequent. I also did a
> vacuum analyze to no effect.

How do you "not allow" deletes? Does this happen because of a failed
foreign key? If so, you can end up with dead tuples. I'd look at
the output of VACUUM VERBOSE to make sure you don't have a lot of
dead tuples. That said, I wonder if fiddling with the statistics on
your tables might help.

A

--
Andrew Sullivan | ajs(at)crankycanuck(dot)ca
In the future this spectacle of the middle classes shocking the avant-
garde will probably become the textbook definition of Postmodernism.
--Brad Holland