On Mon, 28 Oct 2024 at 17:58, Heikki Linnakangas <hlinn...@iki.fi> wrote: > > - The Query message sends an LSN to wait for. (This doesn't handle the > > extended query protocol yet.) > > I'd suggest adding a new message type for this, so that it works the > same with simple and extended query. Or if you just want to wait without > issuing any query.
I imagine a libpq interface like this. lsn = PQcurrentLSN(primaryConn) PQsendWaitLSN(secondaryConn, lsn) PQsendQuery(secondaryConn, ...) One thing I'm wondering is if the current lsn could be a read-only GUC that is reported through ParameterStatus. Because a downside of making it part of ReadyForQuery is that you only get a ReadyForQuery at the end of a pipeline, while a pipeline can contain multiple commits if you use explicit BEGIN/COMMIT in your pipeline. It might be nice to be able to wait on those commits before you've received ReadyForQuery. On the other hand, that seems like a rather exotic usecase that maybe is not worth thinking about too much.
