How to check the replication delay in PostgreSQL?

Question

I would like to measure time between insert data into master-table and slave-table using streaming replication in PostgreSQL 9.3. For this I create table test_time

Answer 1

on master, you can do select * from pg_stat_replication;
this will give you:

|  sent_lsn   |  write_lsn  |  flush_lsn  | replay_lsn  

-+-------------+-------------+-------------+-------------

 | 8D/2DA48000 | 8D/2DA48000 | 8D/2DA48000 | 89/56A0D500 

those can tell you where your offsets are. as you can see from this example, replay on the replica is behind.