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Re: [HACKERS] Slow count(*) again... - Mailing list pgsql-performance

From David Wilson
Subject Re: [HACKERS] Slow count(*) again...
Date
Msg-id AANLkTi=A-70EgJ8yWDCn4hbyCaA0nFJFA3+zedan=nLS@mail.gmail.com
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In response to Re: [HACKERS] Slow count(*) again...  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: [HACKERS] Slow count(*) again...  (Samuel Gendler <sgendler@ideasculptor.com>)
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On Thu, Feb 3, 2011 at 6:05 PM, Robert Haas <robertmhaas@gmail.com> wrote:

If you want to randomly pick 10,000 rows out of all the rows that are
going to be inserted in the table without knowing in advance how many
there will be, how do you do that?

Reservoir sampling, as the most well-known option: http://en.wikipedia.org/wiki/Reservoir_sampling

--
- David T. Wilson
david.t.wilson@gmail.com

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