Peter Eisentraut <peter_e@gmx.net> writes:
> The following command sequence appears to lock up the database system:
> BEGIN;
> LOCK pg_authid;
> PREPARE TRANSACTION 'foo';
> \q
> After that you can't connect anymore, even in single-user mode. The
> only way I could find is to clear out the pg_twophase directory, but
> I'm not sure whether it is safe to do that.
> Should this be prevented somehow, and is there a better recovery path?
AFAICS this is just one of many ways in which a superuser can shoot
himself in the foot; I'm not eager to try to prevent it.
Right offhand, clearing pg_twophase while the system is stopped should
be safe enough.
regards, tom lane