Re: On login trigger: take three

po 14. 9. 2020 v 17:53 odesílatel Konstantin Knizhnik <
k(dot)knizhnik(at)postgrespro(dot)ru> napsal:

>
>
> On 14.09.2020 17:34, Pavel Stehule wrote:
>
> If we introduce buildin session trigger , we should to define what is the
> session. Your design is much more related to the process than to session.
> So the correct name should be "process_start" trigger, or some should be
> different. I think there are two different events - process_start, and
> session_start, and there should be two different event triggers. Maybe the
> name "session_start" is just ambiguous and should be used with a different
> name.
>
>
> I agree.
> I can rename trigger to backend_start or process_start or whatever else.
>

Creating a good name can be hard - it is not called for any process - so
maybe "user_backend_start" ?

>
>
>>
>> 5. I do not quite understand your concern. If I define trigger
>> procedure which is blocked (for example as in your example), then I can
>> use pg_cancel_backend to interrupt execution of login trigger and
>> superuser can login. What should be changed here?
>>
>
> You cannot run pg_cancel_backend, because you cannot open a new session.
> There is a cycle.
>
>
> It is always possible to login by disabling startup triggers using
> disable_session_start_trigger GUC:
>
> psql "dbname=postgres options='-c disable_session_start_trigger=true'"
>

sure, I know. Just this behavior can be a very unpleasant surprise, and my
question is if it can be fixed. Creating custom libpq variables can be the
stop for people that use pgAdmin.