| From: | Nikolas Everett <nik9000(at)gmail(dot)com> |
|---|---|
| To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | sthomas(at)peak6(dot)com, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: Best way to get the latest revision from a table |
| Date: | 2011-01-15 01:50:02 |
| Message-ID: | AANLkTikgQ8y4=5Ly_x+U0mQ7RRHprPGDd-rR8z1NOPWS@mail.gmail.com |
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| Lists: | pgsql-performance |
On Fri, Jan 14, 2011 at 7:59 PM, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov
> wrote:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> > Shaun's example is a bit off
>
> > As for speed, either one might be faster in a particular
> > situation.
>
> After fixing a mistake in my testing and learning from Tom's example
> I generated queries against the OP's test data which produce
> identical results, and I'm finding no significant difference between
> run times for the two versions. The OP should definitely try both
> against the real tables.
>
> <snip>
> -Kevin
>
After trying both against the real tables DISTINCT ON seems to be about two
orders of magnitude faster than the other options.
Thanks so much!
Nik Everett
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