count() in 9.2

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От Steve Horn
Тема count() in 9.2
Дата
Msg-id CAFLkBaVjm9sF38ew_3quhKb7DRn_b5fBghJmgmda=rbB5jYW1Q@mail.gmail.com
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Ответы Re: count() in 9.2  (Simon Riggs <simon@2ndQuadrant.com>)
Re: count() in 9.2  (Thomas Kellerer <spam_eater@gmx.net>)
Список pgsql-novice
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One of the reasons that my team could not take advantage of PostgreSQL was due to the poor performance of count(*) aggregate function.

I visited the "Slow Counting" page on the wiki (http://wiki.postgresql.org/wiki/Slow_Counting) and it states:
"Note that the following article only applies to versions of PostgreSQL prior to 9.2. Index-only scans are now implemented."

So does this mean that count() is no longer slow? If not, how much faster is it? And what does it mean when it says "Index-only scans are now implemented."?

Thanks for your help!

--
Steve Horn

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