Re: Lock problem

From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Victor Sterpu
Sent: Wednesday, April 02, 2014 11:19 AM
To: pgsql-general(at)postgresql(dot)org
Subject: [GENERAL] Lock problem

Hello
 
I have a problem that it seems to be very hard to debug.
Problem is from some postgresql locks. I use PostgreSQL 9.1.8.
 
I runned this query to fid the locks:
SELECT bl.pid AS blocked_pid,
a.usename AS blocked_user,
kl.pid AS blocking_pid,
ka.usename AS blocking_user,
a.current_query AS blocked_statement
FROM pg_catalog.pg_locks bl
JOIN pg_catalog.pg_stat_activity a ON a.procpid = bl.pid
JOIN pg_catalog.pg_locks kl ON kl.transactionid = bl.transactionid AND kl.pid != bl.pid
JOIN pg_catalog.pg_stat_activity ka ON ka.procpid = kl.pid
WHERENOT bl.granted;
The result is a recursive lock.
Pid 10665 is blocked by pid 9844 and pid 9844 is blocked by 10665.
These 2 inserts are in 2 separate transactions.
Can this be a postgresql bug?
 
blocked_pid
blocked_user
blocking_statement
blocking_duration
blocking_pid
blocking_user
blocked_statement
blocked_duration
10665
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1074986, 10.4, 15,15,0, now(), now(), NULL, null, null, NULL, NULL )
00:47:33.995919
9844
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1075033, 248.54, 10,17,0, now(), now(), NULL, null, null, NULL, NULL )
00:37:36.175607
9844
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1075033, 248.54, 10,17,0, now(), now(), NULL, null, null, NULL, NULL )
00:37:36.175607
10665
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1074986, 10.4, 15,15,0, now(), now(), NULL, null, null, NULL, NULL )
00:47:33.995919
10665
postgres
<IDLE> in transaction
00:55:42.876538
9830
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1075033, 248.54, 10,17,0, now(), now(), NULL, null, null, NULL, NULL )
00:37:36.175607
10680
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1075033, 248.54, 10,17,0, now(), now(), NULL, null, null, NULL, NULL )
00:37:36.175607
10665
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1075033, 248.54, 10,17,0, now(), now(), NULL, null, null, NULL, NULL )
00:31:47.211123
9844
postgres
<IDLE> in transaction
00:55:42.876538
9830
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1074986, 10.4, 15,15,0, now(), now(), NULL, null, null, NULL, NULL )
00:47:33.995919
10706
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1074986, 10.4, 15,15,0, now(), now(), NULL, null, null, NULL, NULL )
00:47:33.995919
9844
postgres
INSERT INTO paraclinic_results VALUES (DEFAULT,1074986, 10.4, 15,15,0, now(), now(), NULL, null, null, NULL, NULL )
00:18:45.763758
 
I never use LOCK command in my application.
All locks are made by postgresql.
I use transactional support a lot.
Can someoane give some advice about how can I prevent this locking?
 
Thank you.
 

So, did you check (in pg_stat_activity) what pid 9830 is doing, because looks like this session is holding other sessions.
I don't see " recursive lock" in your query output.

Regards,
Igor Neyman