Re: slow plan for min/max

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От Neil Conway
Тема Re: slow plan for min/max
Дата
Msg-id 1063046951.9051.68.camel@tokyo
обсуждение исходный текст
Ответ на Re: slow plan for min/max  ("scott.marlowe" <scott.marlowe@ihs.com>)
Ответы Re: slow plan for min/max  ("scott.marlowe" <scott.marlowe@ihs.com>)
Список pgsql-performance
On Mon, 2003-09-08 at 11:56, scott.marlowe wrote:
> Basically, Postgresql uses an MVCC locking system that makes massively
> parallel operation possible, but costs in certain areas, and one of those
> areas is aggregate performance over large sets.  MVCC makes it very hard
> to optimize all but the simplest of aggregates, and even those
> optimzations which are possible would wind up being quite ugly at the
> parser level.

As was pointed out in a thread a couple days ago, MIN/MAX() optimization
has absolutely nothing to do with MVCC. It does, however, make
optimizing COUNT() more difficult.

-Neil



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