On Wed, Mar 29, 2023 at 5:13 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > 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?
I think we can send the plain DDL command string and the search_path if we don't insist on applying it in the first version. Maybe the deparser can be integrated later when we're confident that it's ready/subset of it is ready. > > 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 Regards, Zane
