Re: Shouldn't the planner have a higher cost for reverse index scans? - Mailing list pgsql-performance

Tom,

>> Now, while index scans (for indexes on disk) aren't 100% sequential
>> reads, it seems like we should be increasing (substantially) the
>> estimated cost of reverse index scans if the index is likely to be on
>> disk.  No?
>
> AFAICS this is already folded into random_page_cost.

Not as far as I can tell.   It looks to me like the planner is assuming
that a forwards index scan and a reverse index scan will have the same
cost.

--
Josh Berkus
PostgreSQL Experts Inc.
www.pgexperts.com