From: Kyle Cordes <kyle@kylecordes.com>
To: pgsql-performance@postgresql.org
Subject: Re: 8.1 count(*) distinct: IndexScan/SeqScan
Date: Thu, 24 Nov 2005 21:15:44 -0600
Message-ID: <438681E0.6070006@kylecordes.com> (raw)
In-Reply-To: <17380.1132886273@sss.pgh.pa.us>
References: <334D9941-B5B3-4D18-8312-F85D0FB054ED@rilk.com>
<A6F55E12-4479-49F6-B3EE-8CFCC8541179@rilk.com>
<17380.1132886273@sss.pgh.pa.us>
Tom Lane wrote:
>What "same result"? You only ran it up to 2K rows, not 2M. In any
>case, EXPLAIN without ANALYZE is pretty poor ammunition for complaining
>that the planner made the wrong choice. I ran the same
>
Hello, sorry to jump in mid-stream, but this reminded me of something.
I have hit cases where I have a query for which there is a somewhat
"obvious" (to a human...) query plan that should make it possible to get
a query answer pretty quickly. Yet the query "never" finishes (or
rather, after hours of waiting I finally kill it). I assume this is
because of a sub-optimal query plan. But, it appears that an EXPLAIN
ANALYZE runs the actual query, so it takes as long as the actual query.
In such a case, how can I go about tracking down the issue, up to an
including a complaint about the query planner? :-)
(Overall, I'm pretty pleased with the PG query planner; it often gets
better results than another, popular commercial DBMS we use here....
that is just a general impression, not the result of setting up the same
schema in each for a comparison.)
Kyle Cordes
www.kylecordes.com
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-performance@postgresql.org
Cc: kyle@kylecordes.com
Subject: Re: 8.1 count(*) distinct: IndexScan/SeqScan
In-Reply-To: <438681E0.6070006@kylecordes.com>
* 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