I have seen pg_cron but it is not what I am looking for. It schedules
tasks only by time. I am looking for a fifo queue. pg_cron neither
prevents from simultaneous runs I believe.
Quoting Thomas Kellerer <spam_eater@gmx.net>:
> There is no built-in scheduler, but there is an extension that supplies that
>
> https://github.com/citusdata/pg_cron