Re: [COMMITTERS] pgsql: Provide much better wait information in pg_stat_activity.

On Thu, Mar 10, 2016 at 3:44 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> 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

At this point, I get:

rhaas=# select query, state, wait_event, wait_event_type from pg_stat_activity;
query
| state | wait_event | wait_event_type
-------------------------------------------------------------------------+--------+---------------+-----------------
select query, state, wait_event, wait_event_type from
pg_stat_activity; | active | |
select * from foo for update;
| active | transactionid | Lock
(2 rows)

...which looks right to me.

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

I don't see how you can do this here - the session is blocked.

There could well be a bug here, but I need a little more help to find it.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company