| From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
|---|---|
| To: | Antal Attila <atesz(at)ritek(dot)hu> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Wrong plan for subSELECT with GROUP BY |
| Date: | 2006-05-12 19:12:13 |
| Message-ID: | 20060512191213.GS6201@pervasive.com |
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| Thread: | |
| Lists: | pgsql-performance |
If you wrap the LIMIT select into a subquery in the FROM the planner
might figure it out...
SELECT ...
FROM (SELECT blah FROM a LIMIT 10)
LEFT JOIN ...
Unlike some other databases that will spend huge amounts of time on
trying to re-arrange queries and then hope they can effectively cache
query plans, PostgreSQL prefers not to spend cycles on more esoteric
cases so that query planning is fast.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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