Re: dropdb --force - Mailing list pgsql-hackers

On Mon, Oct 21, 2019 at 2:15 PM Pavel Stehule <pavel.stehule@gmail.com> wrote:
>
> po 21. 10. 2019 v 10:25 odesílatel Amit Kapila <amit.kapila16@gmail.com> napsal:
>>
>>
>> Sorry, but I am not able to understand the reason.  Are you worried
>> about the comments atop CountOtherDBBackends which says it is used in
>> Drop Database and related commands?
>
>
> no, just now the code in dropdb looks like
>
> if (force)
>     TerminateOtherDBBackends(...);
>
> CountOtherDBBackends(...);
>
> if I call CountOtherDBBackends from TerminateOtherDBBackends, then code will look like
>
> if (force)
>   TerminateOtherDBBackends(...);
> else
>   CountOtherDBBackends(...);
>
> That looks like CountOtherDBBackends is not called when force clause is active. And this is not true.
>

Hmm, can't we pass force as a parameter to TerminateOtherDBBackends()
and then take the decision inside that function?  That will make the
code of dropdb function a bit simpler.

> So I prefer current relations between routines.
>
>
>
>>
>> > But I can (and I have not any problem with it) remove or significantly decrease sleeping time in
TerminateOtherDBBackends.
>> >
>> > 100 ms is maybe very much - but zero is maybe too low. If there will not be any time between
TerminateOtherDBBackendsand CountOtherDBBackends, then probably CountOtherDBBackends hit waiting 100ms. 
>> >
>> > What about only 5 ms sleeping in TerminateOtherDBBackends?
>> >
>>
>> I am not completely sure about what is the most appropriate thing to
>> do, but I favor removing sleep from TerminateOtherDBBackends.  OTOH,
>> there is nothing broken with the logic.  Anyone else wants to weigh in
>> here?
>
>
> ok. But when I remove it, should not be better to set waiting in  CountOtherDBBackends to some smaller number than
100ms?
>

CountOtherDBBackends is called from other places as well, so I don't
think it is advisable to change the sleep time in that function.
Also, I don't want to add a parameter for it.  I think you have a
point that in some cases we might end up sleeping for 100ms when we
could do with less sleeping time, but I think it is true to some
extent today as well.  I think we can anyway change it in the future
if there is a problem with the sleep timing, but for now, I think we
can just call CountOtherDBBackends after sending SIGTERM and call it
good.  You might want to add a futuristic note in the code.


--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com