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


-----------
OnGres