Re: count * performance issue

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От Matthew
Тема Re: count * performance issue
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Msg-id Pine.LNX.4.64.0803111407580.20402@aragorn.flymine.org
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Ответ на Re: count * performance issue  (Tino Wildenhain <tino@wildenhain.de>)
Ответы Re: count * performance issue  ("Heikki Linnakangas" <heikki@enterprisedb.com>)
Re: count * performance issue  (Andrew Sullivan <ajs@crankycanuck.ca>)
Список pgsql-performance
On Tue, 11 Mar 2008, Tino Wildenhain wrote:
>> And certain, qualified definitions of "accurate" as well. Race condition?
>
> You mean in a three-state-logic? null, not null and something different?

True, False, and FILE_NOT_FOUND.

No, actually I was referring to a race condition. So, you find the count
of rows with IS NULL, then someone changes a row, then you find the count
of rows with IS NOT NULL. Add the two together, and there may be rows that
were counted twice, or not at all.

Matthew

--
It's one of those irregular verbs - "I have an independent mind," "You are
an eccentric," "He is round the twist."
                                      -- Bernard Woolly, Yes Prime Minister

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