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Re: Why count(*) doest use index? - Mailing list pgsql-general

From John R Pierce
Subject Re: Why count(*) doest use index?
Date
Msg-id 4D72BD57.8090801@hogranch.com
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In response to Re: Why count(*) doest use index?  (Allan Kamau <kamauallan@gmail.com>)
Responses Re: Why count(*) doest use index?  (Willy-Bas Loos <willybas@gmail.com>)
Re: Why count(*) doest use index?  (Allan Kamau <kamauallan@gmail.com>)
List pgsql-general
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On 03/05/11 2:05 PM, Allan Kamau wrote:
> Is it possible in theory to efficiently perform count the primary or
> unique indices underlying data structures, regardless whether there is
> a WHERE clause detailing filtration base on values from such index or
> not?

indexes are not exact, due to possibly constant changes in the current
number of visible elements in the relation.

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