| From: | Don Baccus <dhogaza(at)pacifier(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, The Hermit Hacker <scrappy(at)hub(dot)org> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, tech-fyi(at)hub(dot)org |
| Subject: | Re: intelligence in writing a query ... |
| Date: | 2001-05-30 22:53:36 |
| Message-ID: | 3.0.1.32.20010530155336.016deb20@mail.pacifier.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
At 05:35 PM 5/30/01 -0400, Tom Lane wrote:
>Also, since status.gid is (I assume) unique, what's the use of the
>DISTINCT clause at the top level? Seems like that's costing you
>a useless sort & unique pass ...
>> 2EXPLAIN SELECT distinct s.gid, s.created, count(i.title) AS images
...
>> GROUP BY s.gid,s.created
He's already paying for a sort due to the GROUP BY but of course that
makes the DISTINCT meaningless since s.gid and s.created are already
grouped...
- Don Baccus, Portland OR <dhogaza(at)pacifier(dot)com>
Nature photos, on-line guides, Pacific Northwest
Rare Bird Alert Service and other goodies at
http://donb.photo.net.
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