Re: [HACKERS] Re: [COMMITTERS] pgsql: Remove pgbench "progress" testpending solution of its timing is (fwd)

On 12/07/18 19:00, Fabien COELHO wrote:
>>> How pgbenchs prints a progress if none were printed, or if the last
>>> progress was over 0.5 seconds ago, so as to have kind of a catchup in the
>>> end.
>>
>> I don't understand the 0.5 second rule. For the tests, we only need to ensure
>> that at least one progress report is printed, right?
> 
> I'm not so sure;-) I do not want to trust the threadRun loop in case of
> heavy load or whatever issue a run may encounter, so this approach ensures
> that structurally there is always one output even of the whole loop went
> very wrong.

I still don't understand.

For the testing, we just need to make sure that at least one progress 
report is always printed, if -P is used. Right? So where does the 0.5 
second rule come in? Can't we just do "if (no progress reports were 
printed) { print progress report; }" at the end?

> It also adds a small feature which is that there is always a final
> progress when the run is completed, which can be useful when computing
> progress statistics, otherwise some transactions could not be reported in
> any progress at all.

Any transactions in the last 0.5 seconds might still not get reported in 
any progress reports.

>>> when there is nothing to do. This ensures that the -T 2 tap test runs for
>>> at least 2 seconds, whatever. If the host is overload it might be more,
>>> but it cannot be less unless something was wrong.
>>
>> If you want to write a test that checks that a two-second test takes at least
>> two seconds, can't you just not use throttling in that test?
> 
> Indeed… but then throttling would not be tested:-) The point of the test
> is to exercise all time-related options, including throttling with a
> reasonable small value.

Ok. I don't think that's really worthwhile. If we add some code that 
only runs in testing, then we're not really testing the real thing. I 
wouldn't trust the test to tell much. Let's just leave out that magic 
environment variable thing, and try to get the rest of the patch finished.

- Heikki