Re: pgbench - allow to specify scale as a size

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От
Tom Lane
Тема
Re: pgbench - allow to specify scale as a size
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22447.1518887837@sss.pgh.pa.us
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pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Erik Rijkers <er@xs4all.nl>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Tom Lane <tgl@sss.pgh.pa.us>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Alvaro Hernandez <aht@ongres.com>
Re: pgbench - allow to specify scale as a size Tom Lane <tgl@sss.pgh.pa.us>
Re: pgbench - allow to specify scale as a size Alvaro Hernandez <aht@ongres.com>
Re: pgbench - allow to specify scale as a size Mark Wong <mark@2ndQuadrant.com>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Re: pgbench - allow to specify scale as a size Alvaro Hernandez <aht@ongres.com>
Re: pgbench - allow to specify scale as a size Fabien COELHO <coelho@cri.ensmp.fr>
Alvaro Hernandez  writes:
> On 17/02/18 11:26, Tom Lane wrote:
>> Fabien COELHO  writes:
>>> Here is a attempt at extending --scale so that it can be given a size.

>> I do not actually find this to be a good idea.  It's going to be
>> platform-dependent, or not very accurate, or both, and thereby
>> contribute to confusion by making results less reproducible.
>> 
>> Plus, what do we do if the backend changes table representation in
>> some way that invalidates Kaarel's formula altogether?  More confusion
>> would be inevitable.

>      Why not then insert a "few" rows, measure size, truncate the table, 
> compute the formula and then insert to the desired user requested size? 
> (or insert what should be the minimum, scale 1, measure, and extrapolate 
> what's missing). It doesn't sound too complicated to me, and targeting a 
> size is something that I believe it's quite good for user.

Then you'd *really* have irreproducible results.

			regards, tom lane

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