From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: Guillaume Smet <guillaume.smet@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Any idea on how to improve the statistics estimates for this plan?
Date: Fri, 07 Dec 2012 23:16:45 -0500
Message-ID: <2904.1354940205@sss.pgh.pa.us> (raw)
In-Reply-To: <CAMkU=1x9GoZb_6HQf3sF=mN6NEJhwRFsJMO1AwJBh0nDk34sJQ@mail.gmail.com>
References: <CALt0+o9EdN9HDWuzNO2-+Y4XWU6OT03jzvHdzOCrHsLa5dgyMQ@mail.gmail.com>
<CAMkU=1x9GoZb_6HQf3sF=mN6NEJhwRFsJMO1AwJBh0nDk34sJQ@mail.gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
Jeff Janes <jeff.janes@gmail.com> writes:
> The trivial answer to "why" is that it thinks that the vast majority
> of the 33914 rows from the hash join will find no partners in r, but
> in fact each has about 10 partner in r. Why does it think that?
I'm wondering if maybe the vast majority of the rows indeed have no join
partners, but there are a small number with a large number of partners.
The statistics might miss these, if so.
regards, tom lane
--
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
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: tgl@sss.pgh.pa.us, jeff.janes@gmail.com, guillaume.smet@gmail.com
Subject: Re: Any idea on how to improve the statistics estimates for this plan?
In-Reply-To: <2904.1354940205@sss.pgh.pa.us>
* 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