On 2020/10/01 21:14, Bharath Rupireddy wrote:
On Wed, Sep 30, 2020 at 11:32 PM Fujii Masao
<masao.fu...@oss.nttdata.com> wrote:
And another way, if we don't want to use wait_pid() is to have a
plpgsql stored procedure, that in a loop keeps on checking for the
backed pid from pg_stat_activity, exit when pid is 0. and then proceed
to issue the next foreign table query. Thoughts?
+1 for this approach! We can use plpgsql or DO command.
Used plpgsql procedure as we have to use the procedure 2 times.
mypid = -1;
while (mypid != 0)
SELECT pid INTO mypid FROM pg_stat_activity WHERE backend_type =
'client backend' AND application_name = 'fdw_retry_check';
Or we can just wait for the number of processes with
appname='fdw_retry_check' to be zero rather than checking the pid.
Done.
Attaching v7 patch with above changes. Please review it.
Thanks for updating the patch!
+-- committed the txn. The entry of the terminated backend from pg_stat_activity
+-- would be removed only after the txn commit.
pg_stat_clear_snapshot() can be used to reset the entry.
+ EXIT WHEN proccnt = 0;
+ END LOOP;
Isn't it better to sleep here, to avoid th busy loop?
So what I thought was something like
CREATE OR REPLACE PROCEDURE wait_for_backend_termination()
LANGUAGE plpgsql
AS $$
BEGIN
LOOP
PERFORM * FROM pg_stat_activity WHERE application_name =
'fdw_retry_check';
EXIT WHEN NOT FOUND;
PERFORM pg_sleep(1), pg_stat_clear_snapshot();
END LOOP;
END;
$$;
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
