test=# SELECT (x).pid, (x).backend_type FROM (SELECT pg_stat_get_activity(NULL) AS x) AS y;
 pid  |         backend_type
------+------------------------------
 4924 | autovacuum launcher
 4946 | logical replication launcher
 5086 | client backend
 4922 | background writer
 4921 | checkpointer
 4923 | walwriter
(6 rows)