From: Andrew Sullivan <andrew@libertyrms.info>
To: pgsql-performance@postgresql.org
Subject: Re: An unresolved performance problem.
Date: Thu, 8 May 2003 07:20:20 -0400
Message-ID: <20030508112020.GB3728@libertyrms.info> (raw)
In-Reply-To: <Pine.LNX.4.44.0305081013350.422-100000@matrix.gatewaynet.com>
References: <Pine.LNX.4.44.0305071700530.28446-100000@matrix.gatewaynet.com>
<Pine.LNX.4.44.0305081013350.422-100000@matrix.gatewaynet.com>
On Thu, May 08, 2003 at 10:48:52AM -0200, Achilleus Mantzios wrote:
> That is, we have a marginal decrease of the total cost
> for the index scan when random_page_cost = 1.9,
> whereas the "real cost" in the means of total runtime
> ranges from 218 msecs (seq scan) to 19 msecs (index scan).
> (is it sane?)
You're right that the problem is the poor estimate of the cost of
that selection. I recall you mentioning that you'd expanded the
statistics on the field, but I don't recall to what. I know that
under some circumstances, you _really_ have to increase the stats to
get a meaningful sample.
A
--
----
Andrew Sullivan 204-4141 Yonge Street
Liberty RMS Toronto, Ontario Canada
<andrew@libertyrms.info> M2P 2A8
+1 416 646 3304 x110
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: andrew@libertyrms.info, pgsql-performance@postgresql.org
Subject: Re: An unresolved performance problem.
In-Reply-To: <20030508112020.GB3728@libertyrms.info>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox