Re: Rethinking stats communication mechanisms

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От
Bort, Paul
Тема
Re: Rethinking stats communication mechanisms
Дата
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DB106B1B5B8F734B8FF3E155A3A556C202D4FBF5@clemail1.tmwsystems.com
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Rethinking stats communication mechanisms Tom Lane <tgl@sss.pgh.pa.us>
Re: Rethinking stats communication mechanisms "Magnus Hagander" <mha@sollentuna.net>
Re: Rethinking stats communication mechanisms Tom Lane <tgl@sss.pgh.pa.us>
Re: Rethinking stats communication mechanisms Hannu Krosing <hannu@skype.net>
Re: Rethinking stats communication mechanisms "Magnus Hagander" <mha@sollentuna.net>
Re: Rethinking stats communication mechanisms PFC <lists@peufeu.com>
Re: Rethinking stats communication mechanisms Tom Lane <tgl@sss.pgh.pa.us>
Re: Rethinking stats communication mechanisms Tom Lane <tgl@sss.pgh.pa.us>
Re: Rethinking stats communication mechanisms Kenneth Marshall <ktm@it.is.rice.edu>
Re: Rethinking stats communication mechanisms "Bort, Paul" <pbort@tmwsystems.com>
Re: Rethinking stats communication mechanisms Tom Lane <tgl@sss.pgh.pa.us>
Re: Rethinking stats communication mechanisms Kenneth Marshall <ktm@it.is.rice.edu>
Re: Rethinking stats communication mechanisms "Bort, Paul" <pbort@tmwsystems.com>
Re: Rethinking stats communication mechanisms PFC <lists@peufeu.com>
Re: Rethinking stats communication mechanisms Greg Stark <gsstark@mit.edu>
Re: Rethinking stats communication mechanisms Douglas McNaught <doug@mcnaught.org>
Re: Rethinking stats communication mechanisms Greg Stark <gsstark@mit.edu>
Re: Rethinking stats communication mechanisms Douglas McNaught <doug@mcnaught.org>
Re: Rethinking stats communication mechanisms Greg Stark <gsstark@mit.edu>
> 
> * reader's read starts before and ends after writer's update: reader
> will certainly note a change in update counter.
> 
> * reader's read starts before and ends within writer's update: reader
> will note a change in update counter.
> 
> * reader's read starts within and ends after writer's update: reader
> will note a change in update counter.
> 
> * reader's read starts within and ends within writer's update: reader
> will see update counter as odd.
> 
> Am I missing anything?
> 

The only remaining concern would be the possibility of the reader
thrashing because the writer is updating so often that the reader never
gets the same counter twice. IIRC, the reader was only sampling, not
trying to catch every entry, so that will help. But is it enough?

Regards,
Paul Bort

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