Using additional information in pg_stat_activity

Before PostgreSQL 10.0, pg_stat_activity only contained information about normal backend processes serving end users (connections). However, this has changed. Since PostgreSQL 10.0, a lot more information is exposed. It is possible to figure out what these other system processes are doing.

The following listing shows the content of  pg_stat_activity on an idle database instance:

test=# \x 
Expanded display is on. 

test=# SELECT pid, wait_event_type, wait_event, backend_type  
   FROM  pg_stat_activity ;
 
-[ RECORD 1 ]---+-------------------- 
pid             | 12159 
wait_event_type | Activity 
wait_event      | AutoVacuumMain 
backend_type    | autovacuum launcher 
-[ RECORD 2 ]---+-------------------- 
pid             | 12161 
wait_event_type | Activity 
wait_event      | LogicalLauncherMain 
backend_type    | background worker 
-[ RECORD 3 ]---+-------------------- 
pid             | 12628 
wait_event_type |  
wait_event      |  
backend_type    | client backend 
-[ RECORD 4 ]---+-------------------- 
pid             | 12156 
wait_event_type | Activity 
wait_event      | BgWriterMain 
backend_type    | background writer 
-[ RECORD 5 ]---+-------------------- 
pid             | 12155 
wait_event_type | Activity 
wait_event      | CheckpointerMain 
backend_type    | checkpointer 
-[ RECORD 6 ]---+-------------------- 
pid             | 12157 
wait_event_type | Activity 
wait_event      | WalWriterMain 
backend_type    | walwriter 

What you see here is that every server process is listed. It will allow you to gain some insights into what is happening the server.