On Wed, Mar 29, 2023 at 2:49 AM Zheng Li <zhengl...@gmail.com> wrote: > > > I agree that a full fledged DDL deparser and DDL replication is too > big of a task for one patch. I think we may consider approaching this > feature in the following ways: > 1. Phased development and testing as discussed in other emails. > Probably support table commands first (as they are the most common > DDLs), then the other commands in multiple phases. > 2. Provide a subscription option to receive the DDL change, raise a > notice and to skip applying the change. The users can listen to the > DDL notice and implement application logic to apply the change if > needed. The idea is we can start gathering user feedback by providing > a somewhat useful feature (compared to doing nothing about DDLs), but > also avoid heading straight into the potential footgun situation > caused by automatically applying any mal-formatted DDLs. >
Doesn't this mean that we still need to support deparsing of such DDLs which is what I think we don't want? > 3. As cross-version DDL syntax differences are expected to be uncommon > (in real workload), maybe we can think about other options to handle > such edge cases instead of fully automating it? For example, what > about letting the user specify how a DDL should be replicated on the > subscriber by explicitly providing two versions of DDL commands in > some way? > As we are discussing in another related thread [1], if publisher_version > subscriber_version then it may not be possible to form a DDL at publisher which can be applied to the subscriber. OTOH, we need to think if there could be any problems with publisher_version < subscriber_version setup, and if so, what we want to do for it. Once, we have a clear answer to that then I think we will be in a better position to answer your question. [1] - https://www.postgresql.org/message-id/OS0PR01MB5716088E497BDCBCED7FC3DA94849%40OS0PR01MB5716.jpnprd01.prod.outlook.com -- With Regards, Amit Kapila.
