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.Grittner@wicourts.gov> wrote:
Michael Glaesemann <
grzm@seespotcode.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;
*correct* version.
-Kevin
