Hi Andrei
General speaking any DDL (Create, Alter Drop .etc) commands issue exclusive locks automatically, so anything this transaction touches starts getting exclusive locks. Assuming this is a multi-threading app these two threads are sending commands all but at the same time. The Exclusive lock has not been committed yet as its waiting for a previous insert to finish, and the Exclusive lock is blocking the insert as its transaction started prior to the Insert.
the wait queue is pretty long 84, 80, 82, 83, 87, 88, 85, 86.
The time stamps are only 2 ms apart, lots of commands being sent in at nearly the same time...
Here are my suggestions
Tweak the Python app to make sure all the threads have committed their transactions place a lock on all the other threads, Then issue a DDL command, when the command is committed, then unlock the other threads. That should kill off the race condition deadlock..
Post all the SQL code that is creating this exclusive lock, we may be able re-write the SQL code to reduce the time and/or resources this Exclusive Lock is creating.
Pyscopg2 default mode is to require issuing a Commit it does not automatically commit transaction. If running in auto-commit OFF try turning this ON for DDL commands may fix the issue. It may also be that DDL command takes far longer than 1 second to complete...
