Postgres Pro
Downloads
Home   >   mailing lists

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

From Tom Lane
Subject Re: Shouldn't the planner have a higher cost for reverse index scans?
Date
Msg-id 25703.1239383976@sss.pgh.pa.us
Whole thread Raw
In response to Re: Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus <josh@agliodbs.com>)
Responses Re: Shouldn't the planner have a higher cost for reverse index scans?  (Josh Berkus <josh@agliodbs.com>)
Re: Shouldn't the planner have a higher cost for reverse index scans?  (Matthew Wakeling <matthew@flymine.org>)
List pgsql-performance
Tree view 
Josh Berkus <josh@agliodbs.com> writes:
> 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.

Right, because they do.  If you think otherwise, demonstrate it.
(bonnie tests approximating a reverse seqscan are not relevant
to the performance of indexscans.)

            regards, tom lane

pgsql-performance by date:

Previous
From: Josh Berkus
Date:
Subject: Re: Using IOZone to simulate DB access patterns
Next
From: Josh Berkus
Date:
Subject: Re: Using IOZone to simulate DB access patterns