We found out because we are monitoring long running queries, and saw it had been running for a month before the restart yesterday.
I just queried pg_stat_activity and it seems to be running since then.
taimusz=# SELECT pid, query_start, usename, left(query,70)
FROM pg_stat_activity
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'
ORDER BY query_start;
pid | query_start | usename | left
---------+-------------------------------+------------+------------------------------------------------------------------------
2321161 | 2021-05-17 16:15:13.906679+02 | subscriber | SELECT pg_catalog.set_config('search_path', '', false);
You should add: AND state != 'idle' to filter out queries that are no longer running and don't have an open transaction. Your query is finding long running sessions, not necessarily long running queries.
