Re: Somebody has not thought through subscription locking considerations

Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> writes:
> On Fri, Mar 31, 2017 at 9:53 AM, Petr Jelinek
> <petr(dot)jelinek(at)2ndquadrant(dot)com> wrote:
>> On 30/03/17 07:25, Tom Lane wrote:
>>> I await with interest an explanation of what "VACUUM FULL pg_class" is
>>> doing trying to acquire ShareRowExclusiveLock on pg_subscription_rel, not
>>> to mention why a DROP SEQUENCE is holding some fairly strong lock on that
>>> relation.

> VACUUM FULL of any table acquires ShareRowExclusiveLock on
> pg_subscription_rel because when doDeletion removes old heap the
> RemoveSubscriptionRel is called in heap_drop_with_catalog.

This seems entirely horrid: it *guarantees* deadlock possibilities.
And I wonder what happens when I VACUUM FULL pg_subscription_rel
itself.

At the very least, it would be a good idea to exclude the system
catalogs from logical replication, wouldn't it?

regards, tom lane