Re: pgbench - allow to specify scale as a size - Mailing list pgsql-hackers

From Fabien COELHO
Subject Re: pgbench - allow to specify scale as a size
Date
Msg-id alpine.DEB.2.20.1802171833450.20813@lancre
Whole thread Raw
In response to Re: pgbench - allow to specify scale as a size  (Alvaro Hernandez <aht@ongres.com>)
Responses Re: pgbench - allow to specify scale as a size  (Alvaro Hernandez <aht@ongres.com>)
List pgsql-hackers
>     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.

The formula I used approximates the whole database, not just one table. 
There was one for the table, but this is only part of the issue. In 
particular, ISTM that index sizes should be included when caching is 
considered.

Also, index sizes are probably in n ln(n), so some level of approximation 
is inevitable.

Moreover, the intrinsic granularity of TPC-B as multiple of 100,000 rows 
makes it not very precise wrt size anyway.

-- 
Fabien.

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