Jean-Christophe Praud <jc(at)steek(dot)com> writes:
> Indeed, the tables I tried to vacuum have locks on them.
> AccessShareLock belonging to queries which seem sleeping. I tried to
> kill these queries but pg_cancel_backend() has no effect, and the
> process doesn't get the 15 signal.
> How can I get rid of these blocking queries without restarting the
> server ? They are not listed as "waiting" in pg_stat_activity.
Have you tried killing the connected client sessions?
regards, tom lane