| From: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
|---|---|
| To: | Alvaro Hernandez <aht(at)ongres(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: pgbench - allow to specify scale as a size |
| Date: | 2018-02-17 17:37:38 |
| Message-ID: | alpine.DEB.2.20.1802171833450.20813@lancre |
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| Thread: | |
| Lists: | 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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