On Wed, May 26, 2021 at 1:53 PM Petr Jelinek <petr.jeli...@enterprisedb.com> wrote: > > On 26 May 2021, at 05:04, Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > On Tue, May 25, 2021 at 12:40 PM Michael Paquier <mich...@paquier.xyz> > > wrote: > >> > >> It seems to me that the 2PC issues on catalog tables and the issues > >> related to logical replication in synchonous mode are two distinct > >> things that need to be fixed separately. > >> > > > > Fair enough. But the way we were looking at them as they will also > > block (lead to deadlock) for logical replication of prepared > > transactions and also logical replication in synchonous mode without > > prepared transactions. Now, if we want to deal with the 2PC issues > > separately that should be fine as well. However, for that we need to > > see which all operations we want to block on [user]_catalog_tables. > > The first one is lock command, then there are other operations like > > Cluster which take exclusive lock on system catalog tables and we > > allow them to be part of prepared transactions (example Cluster > > pg_trigger using pg_trigger_oid_index;), another kind of operation is > > Truncate on user_catalog_tables. Now, some of these might not allow > > connecting after restart so we might need to think whether we want to > > prohibit all such operations or only some of them. > > > > > IIRC this was discussed the first time 2PC decoding was proposed and > everybody seemed fine with the limitation so I'd vote for just documenting > it, same way as the sync rep issue. >
+1. > If you'd prefer fixing it by blocking something, wouldn't it make more sense > to simply not allow PREPARE if one of these operations was executed, > similarly to what we do with temp table access? > The point was that even if somehow we block for prepare, there doesn't seem to be a simple way for synchronous logical replication which can also have similar problems. So, I would prefer to document it and we can even think to backpatch the sync rep related documentation. Michael seems to be a bit interested in dealing with some of the 2PC issues due to reasons different than logical replication which I am not completely sure is a good idea and Tom also feels that is not a good idea. -- With Regards, Amit Kapila.
