Re: Strange (?) Index behavior?

Allen Landsidel <alandsidel@gmail.com> writes:
> With that many rows, and a normal index on the field, postgres figures
> the best option for say "I%" is not an index scan, but a sequential
> scan on the table, with a filter -- quite obviously this is slow as
> heck, and yes, I've run analyze several times and in fact have the
> vacuum analyze automated.
> With the partial index the index scan is used and the cost drops from
> 0..2million to 0..9000 -- a vast improvement.

Hmm.  This suggests to me that you're using a non-C locale and so a
plain index *can't* be used for a LIKE query.  Can you force it to use
an indexscan by setting enable_seqscan = false?  If not then you've got
a locale problem.  As someone else pointed out, this can be worked
around by creating an index with the right operator class.

            regards, tom lane