PostgreSQL 9.6 introduced new two columns of table pg_stat_activity. The columns are wait_event_type and wait_event.

The column wait_event_type reports the type of event a backend is waiting for, and the wait_event which is the name of the event being waiting for. These both columns are very useful for finding a query event information.

Please check small demonstration of this:

Create a sample table:

CREATE TABLE tbl_students(rno int, name character varying(10));

Put your table in lock mode:

BEGIN TRANSACTION;
LOCK tbl_students IN ACCESS EXCLUSIVE MODE;

Open a new query session, and try to insert a below record:

INSERT INTO tbl_students VALUES (1,'Anvesh');

Open a new query session, and check the output of pg_stat_activity:

SELECT query, wait_event_type, wait_event FROM pg_stat_activity