Re: slow plan for min/max

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От Greg Stark
Тема Re: slow plan for min/max
Дата
Msg-id 87wucj3pe3.fsf@stark.dyndns.tv
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Ответ на Re: slow plan for min/max  ("scott.marlowe" <scott.marlowe@ihs.com>)
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"scott.marlowe" <scott.marlowe@ihs.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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