Re: extend pgbench expressions with functions

Hello Robert,

>> 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.
>
> Sure, we could do that.  But whether it materially changes pgbench -S
> results, say, is a lot more important.

Indeed. Several runs on my laptop:
  ~ 400000-540000 tps with master using:    \set naccounts 100000 * :scale    \setrandom aid 1 :naccounts
  ~ 430000-530000 tps with full function patch using:    \set naccounts 100000 * :scale    \setrandom aid 1 :naccounts
  ~ 730000-890000 tps with full function patch using:    \set aid random(1, 100000 * :scale)

The performance is pretty similar on the same script. The real pain is 
variable management, avoiding some is a win.

However, as you suggest, the tps impact even with -M prepared -S is 
nought, because the internal scripting time in pgbench is much smaller 
than the time to do actual connecting and querying.

-- 
Fabien.