Re: pgbench - allow to specify scale as a size

Hello Mark,

> What if we consider using ascii (utf8?) text file sizes as a reference
> point, something independent from the database?

Why not.

TPC-B basically specifies that rows (accounts, tellers, branches) are all
padded to 100 bytes, thus we could consider (i.e. document) that
--scale=SIZE refers to the amount of useful data hold, and warn that
actual storage would add various overheads for page and row headers, free
space at the end of pages, indexes...

Then one scale step is 100,000 accounts, 10 tellers and 1 branch, i.e.
100,011 * 100 ~ 9.5 MiB of useful data per scale step.

> I realize even if a flat file size can be used as a more consistent
> reference across platforms, it doesn't help with accurately determining
> the final data file sizes due to any architecture specific nuances or
> changes in the backend. But perhaps it might still offer a little more
> meaning to be able to say "50 gigabytes of bank account data" rather
> than "10 million rows of bank accounts" when thinking about size over
> cardinality.

Yep.

Now the overhead is really 60-65%. Although the specification is
unambiguous, but we still need some maths to know whether it fits in
buffers or memory... The point of Karel regression is to take this into
account.

Also, whether this option would be more admissible to Tom is still an open
question. Tom?

--
Fabien.