Re: Application name patch - v4

Dimitri Fontaine <dfontaine(at)hi-media(dot)com> writes:
> Le 29 nov. 2009 18:22, Tom Lane a crit :
>>> I think we should use GUC_NO_RESET_ALL.
>>
>> I agree with you, but it seems we have at least as many votes to not do
>> that. Any other votes out there?

> Driven by the pooler use case (pgbouncer, even), I'd say RESET ALL should reset also the application name. And the connection value is not tied any more to something sensible as soon as you have pooling in there...

The thing is that the libpq API treats application_name as a *property
of the connection*. You shouldn't expect it to go away on RESET ALL,
any more than you'd expect RESET ALL to cause you to be reconnected to
some other database.

If a pooler wants application_name to be cleared when it issues RESET
ALL, I think it ought to be setting the name via SET, not via the libpq
connection option.

But it's certainly true that using GUC_NO_RESET_ALL would be a quick
kluge rather than a proper solution. Andres Freund suggested upthread
that we should fix this by extending SET:

: One possibility would be to make it possible to issue SETs that behave
: as if set in a startup packet - imho its an implementation detail that
: SET currently is used.

I think there's a good deal of merit in this, and it would't be hard at
all to implement, seeing that we already have SET LOCAL and SET SESSION.
We could add a third keyword, say SET DEFAULT, that would have the
behavior of setting the value in a fashion that would persist across
resets. I'm not sure that DEFAULT is exactly le mot juste here, but
agreeing on a keyword would probably be the hardest part of making it
happen.

regards, tom lane