Re: Picking out the most recent row using a time stamp column
| От | Dave Crooke |
|---|---|
| Тема | Re: Picking out the most recent row using a time stamp column |
| Дата | |
| Msg-id | AANLkTimSmjGrCqwZWRXU1_=FW0adbWdxLXMK0n=Vw+Cc@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Picking out the most recent row using a time stamp column ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>) |
| Ответы |
Re: Picking out the most recent row using a time stamp
column
Re: Picking out the most recent row using a time stamp column |
| Список | 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
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.Grittner@wicourts.gov> wrote:
Michael Glaesemann <grzm@seespotcode.net> wrote:Dang! I forgot the DESC in my post! Thanks for showing the
> 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;
*correct* version.
-Kevin
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