| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Shaun Thomas <sthomas(at)peak6(dot)com> |
| Cc: | Dave Crooke <dcrooke(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Michael Glaesemann <grzm(at)seespotcode(dot)net>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Picking out the most recent row using a time stamp column |
| Date: | 2011-02-25 01:52:19 |
| Message-ID: | 4D670B53.70003@agliodbs.com |
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| Thread: | |
| Lists: | pgsql-performance |
> Why did you use row_number instead of rank?
Because I assumed he only wanted one row in the event of ties.
Hmmm, although with that schema, there won't be ties. So it's pretty
much arbitrary then.
> I am now curious how the speed compares though. I still think the
> DISTINCT ON will be faster, but it would be a great surprise.
Hopefully we'll find out! The windowing functions are usually much
faster for me. I think in 9.0 or 9.1 someone replumbed DISTINCT ON to
use a bunch of the window function internals, at which point it'll cease
to matter.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
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