Re: pgsql: Provide much better wait information in pg_stat_activity.

Hi

2016-03-10 19:55 GMT+01:00 Robert Haas <rhaas(at)postgresql(dot)org>:

> Provide much better wait information in pg_stat_activity.
>
> When a process is waiting for a heavyweight lock, we will now indicate
> the type of heavyweight lock for which it is waiting. Also, you can
> now see when a process is waiting for a lightweight lock - in which
> case we will indicate the individual lock name or the tranche, as
> appropriate - or for a buffer pin.
>
> Amit Kapila, Ildus Kurbangaliev, reviewed by me. Lots of helpful
> discussion and suggestions by many others, including Alexander
> Korotkov, Vladimir Borodin, and many others.
>
> Branch
> ------
> master
>
>
I am trying to test this feature, and there I see not actual data. Maybe
this behave is not related to this patch:

create table foo(a int);
insert into foo values(10);

session one:

begin; select * from foo for update;

session two:

begin; select * from foo for update;
session two is waiting

session one:
select * from pg_stat_activity -- I don't see correct information about
session two

session two:
rollback; begin; select * from foo where a = 10 for update;
session two is waiting again

session one:
select * from pg_stat_activity; -- The content is not changed

So content of pg_stat_activity is not correct in holder lock session.
Independent third session see valid content of pg_stat_activity.

Hypothesis: the pg_stat_activity is not refreshed under opened transaction?

Regards

Pavel