From: | Dave Crooke <dcrooke(at)gmail(dot)com> |
---|---|
To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
Cc: | Michael Glaesemann <grzm(at)seespotcode(dot)net>, pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Picking out the most recent row using a time stamp column |
Date: | 2011-02-24 23:38:37 |
Message-ID: | AANLkTimSmjGrCqwZWRXU1_=FW0adbWdxLXMK0n=Vw+Cc@mail.gmail.com |
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Lists: | pgsql-performance |
Thanks to all .... I had a tickling feeling at the back of my mind that
there was a neater answer here. For the record, times (all from in-memory
cached data, averaged over a bunch of runs):
Dependent subquery = 117.9 seconds
Join to temp table = 2.7 sec
DISTINCT ON = 2.7 sec
So the DISTINCT ON may not be quicker, but it sure is tidier.
Cheers
Dave
On Thu, Feb 24, 2011 at 2:24 PM, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov
> wrote:
> Michael Glaesemann <grzm(at)seespotcode(dot)net> wrote:
>
> > SELECT DISTINCT ON (data.id_key)
> > data.id_key, data.time_stamp, data.value
> > FROM data
> > ORDER BY data.id_key, data.time_stamp DESC;
>
> Dang! I forgot the DESC in my post! Thanks for showing the
> *correct* version.
>
> -Kevin
>
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