pg.ddx.io  pgsql-performance@postgresql.org mailing list archive  

help / color / mirror / Atom feed
From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Jarvis <thangalin@gmail.com>
Cc: Thom Brown <thombrown@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Optimize date query for large child tables: GiST or GIN?
Date: Thu, 20 May 2010 16:18:58 -0400
Message-ID: <8132.1274386738@sss.pgh.pa.us> (raw)
In-Reply-To: <AANLkTimLdBWaVpSF5Sc3ArT_9jcAjhNiB9WBBA4HIyXj@mail.gmail.com>
References: <AANLkTimi_Jh4J6bLZ8lZ0cGQ0VVG7XPCKaFN9GRHd6mP@mail.gmail.com>
	<AANLkTimZ9zIEebspkg8Iy8vhEeBhe-JLJeJiYPcW88sJ@mail.gmail.com>
	<AANLkTinTEyf_9ooDHv12vfsIuLihB2VqJ6NZGD2DnyHf@mail.gmail.com>
	<AANLkTimk7lRS8FHJOot3tF-c6Ds4jexCvWKEQNU1V0Xt@mail.gmail.com>
	<7143.1274382139@sss.pgh.pa.us>
	<AANLkTim7O3Aalp31WKwBuTufYXeUMQWkwy51nvRcI0QY@mail.gmail.com>
	<AANLkTikl8wlHPJaArMWO9XWgG0vk9tununw3eUAYh1IC@mail.gmail.com>
	<7767.1274385170@sss.pgh.pa.us>
	<AANLkTikOEC-Gr3eqGlyGauRAZJknQEaS5DEWw-ZOcl6r@mail.gmail.com>
	<7917.1274385834@sss.pgh.pa.us>
	<AANLkTimLdBWaVpSF5Sc3ArT_9jcAjhNiB9WBBA4HIyXj@mail.gmail.com>

David Jarvis <thangalin@gmail.com> writes:
> I was hoping to eliminate this part of the query:
>         (cast(extract( YEAR FROM m.taken ) + greatest( -1 *
>           sign(
>             (extract( YEAR FROM m.taken )||'-12-31')::date -
>             (extract( YEAR FROM m.taken )||'-01-01')::date ), 0
>         ) AS text)||'-12-31')::date

> That uses functions to create the dates, which is definitely the problem.

Well, it's not the functions per se that's the problem, it's the lack of
a useful index on the expression.  But as somebody remarked upthread,
that expression doesn't look correct at all.  Doesn't the whole
greatest() subexpression reduce to a constant?

			regards, tom lane



view thread (44+ messages)  latest in thread

Message-ID: <8132.1274386738@sss.pgh.pa.us>
Permalink:  ../8132.1274386738@sss.pgh.pa.us/
Also on:    postgresql.org/message-id/8132.1274386738@sss.pgh.pa.us

 · 

reply
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, thangalin@gmail.com, thombrown@gmail.com
  Subject: Re: Optimize date query for large child tables: GiST or GIN?
  In-Reply-To: <8132.1274386738@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