Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue - Mailing list pgsql-hackers

Heikki Linnakangas <hlinnaka@iki.fi> writes:
> Fortunately that's easy to fix: We can move the IsListeningOn() check 
> after releasing the lock. See attached.
> The elephant in the room of course is that a lookup in a linked list is 
> O(n) and it would be very straightforward to replace it with e.g. a hash 
> table. We should do that irrespective of this bug fix. But I'm inclined 
> to do it as a separate followup patch.

There is a different patch series that's concerned with improving
NOTIFY throughput [1].  I think this one should just focus on
fixing the XID problem.

            regards, tom lane

[1] https://commitfest.postgresql.org/patch/6078/