Re: extend pgbench expressions with functions

On Tue, Feb 16, 2016 at 9:18 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I experimented with trying to do this and ran into a problem: where
> exactly would you store the evaluated arguments when you don't know
> how many of them there will be? And even if you did know how many of
> them there will be, wouldn't that mean that evalFunc or evaluateExpr
> would have to palloc a buffer of the correct size for each invocation?
> That's far more heavyweight than the current implementation, and
> minimizing CPU usage inside pgbench is a concern. It would be
> interesting to do some pgbench runs with this patch, or the final
> patch, and see what effect it has on the TPS numbers, if any, and I
> think we should. But the first concern is to minimize any negative
> impact, so let's talk about how to do that.

Good point. One simple idea here would be to use a custom pgbench
script that has no SQL commands and just calculates the values of some
parameters to measure the impact without depending on the backend,
with a fixed number of transactions.
--
Michael