> I'm not sure I > get the point of logical replication that requires a physical replica as
> a prerequisite.
> It would be enormously > more performant for the master to be emitting logical replication > records to start with, since it already has all the right names etc > at hand at basically no cost.
I want to emphasize that any system which uses the logical reader setup, including a replication system, tends to be very computationally intensive on the database which it queries all so often. In most of the environments, the source database is the main database, and as such, any performance degradation on this database is very bad.
On the other hand, if we offload almost all the work to the physical replica, our source database, which is the main database, still functions at the same throughput.
Thus, at the cost of having the replication system as a whole run a little slower than it could if it were using the main database, we have made sure that our performance critical main source database is not affected in performance at all.
