| From: | Greg Stark <gsstark(at)mit(dot)edu> |
|---|---|
| To: | "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com> |
| Cc: | Pailloncy Jean-Gérard <pailloncy(at)ifrance(dot)com>, <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: slow plan for min/max |
| Date: | 2003-09-08 22:07:48 |
| Message-ID: | 87wucj3pe3.fsf@stark.dyndns.tv |
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| Lists: | pgsql-performance |
"scott.marlowe" <scott(dot)marlowe(at)ihs(dot)com> writes:
> Basically, Postgresql uses an MVCC locking system that makes massively
As discussed, uh, a few days ago, this particular problem is not caused by
MVCC but by postgres having a general purpose aggregate system and not having
special code for handling min/max. Aggregates normally require access to every
record they're operating on, not just the first or last in some particular
order. You'll note the LIMIT 1/DISTINCT ON work-around works fine with MVCC...
--
greg
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