Skip site navigation (1) Skip section navigation (2)

Re: Random Page Cost and Planner

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "David Jarvis" <thangalin(at)gmail(dot)com>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Random Page Cost and Planner
Date: 2010-05-25 18:28:41
Message-ID: (view raw or whole thread)
Lists: pgsql-performance
David Jarvis <thangalin(at)gmail(dot)com> wrote:
> The value for *random_page_cost* was at 2.0; reducing it to 1.1
> had a massive performance improvement (nearly an order of
> magnitude). While the results now return in 5 seconds (down from
> ~85 seconds)
It sounds as though the active portion of your database is pretty
much cached in RAM.  True?
> problematic lines remain. Bumping the query's end date by a single
> year causes a full table scan
> How do I persuade PostgreSQL to use the indexes, regardless of
> number of years between the two dates?
I don't know about "regardless of the number of years" -- but you
can make such plans look more attractive by cutting both
random_page_cost and seq_page_cost.  Some highly cached loads
perform well with these set to equal values on the order of 0.1 to
> (A full table scan against 43 million rows is probably not the
> best plan.)
It would tend to be better than random access to 43 million rows, at
least if you need to go to disk for many of them.

In response to


pgsql-performance by date

Next:From: Joshua TolleyDate: 2010-05-25 19:01:49
Subject: Re: prepared query performs much worse than regular query
Previous:From: Scott CareyDate: 2010-05-25 18:27:08
Subject: Re: prepared query performs much worse than regular query

Privacy Policy | About PostgreSQL
Copyright © 1996-2015 The PostgreSQL Global Development Group