On Mon, Dec 7, 2020 at 9:25 AM Craig Ringer <craig.rin...@enterprisedb.com> wrote: > > Hi folks > > Now that we're well on track for streaming logical decoding, it's becoming > more practical to look at parallel logical apply. > > The support for this in pglogical3 benefits from a deadlock detector hook. It > was added in the optional patched postgres pglogical can use to enable > various extra features that weren't possible without core changes, but isn't > present in community postgres yet. > > I'd like to add it. > > The main benefit is that it lets the logical replication support tell the > deadlock detector that it should prefer to kill the victim whose txn has a > higher upstream commit lsn. That helps encourage parallel logical apply to > make progress in the face of deadlocks between concurrent txns. > > Any in-principle objections? >
I think it will depend on your exact proposal of the hook but one thing we might want to consider is whether it is acceptable to invoke third-party code after holding LWLocks. We acquire LWLocks in CheckDeadLock and then run the deadlock detector code. Also, it might be better if you can expand the use case a bit more. It is not very clear from what you have written. -- With Regards, Amit Kapila.
