See postgres connections

psql_connections.sql

SELECT state, COUNT(*) FROM pg_stat_activity  
WHERE pid <> pg_backend_pid() 
GROUP BY 1;

#         state        | count
# ---------------------+-------
#  active              |     7
#  idle                |   569
#  idle in transaction |     2
#                      |     9
# (4 rows)

SELECT application_name, COUNT(*) FROM pg_stat_activity  
WHERE pid <> pg_backend_pid() 
GROUP BY 1 ORDER BY 1;

#                       application_name                      | count
# ------------------------------------------------------------+-------
#  web_server                                                 |    63
#  cron_job                                                   |     1
#  psql                                                       |     4
#  background_job                                             |    15
# (4 rows)