Re: pgbench - allow to specify scale as a size

On 17/02/18 12:37, Fabien COELHO wrote:
>
>>     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.
>

    Sure, makes sense, so my second suggestion seems more reasonable:
insert with scale 1, measure there (ok, you might need to crete indexes
only to later drop them), and if computed scale > 1 then insert whatever
is left to insert. Shouldn't be a big deal to me.

    I like the feature :)

    Álvaro

--

Alvaro Hernandez

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OnGres