On 2020-Jun-03, Andres Freund wrote: > I don't think we should prohibit this. For one, it'd probably break some > clients, without a meaningful need.
There *is* a need, namely to keep complexity down. This is quite convoluted, it's got a lot of historical baggage because of the way it was implemented, and it's very difficult to understand. The greatest motive I see is to make this easier to understand, so that it is easier to modify and improve in the future. > But I think it's also actually quite useful to be able to access > catalogs before streaming data. You e.g. can look up configuration of > the primary before streaming WAL. With a second connection that's > actually harder to do reliably in some cases, because you need to be > sure that you actually reached the right server (consider a pooler, > automatic failover etc). I don't think having a physical replication connection access catalog data directly is a great idea. We already have gadgets like IDENTIFY_SYSTEM for physical replication that can do that, and if you need particular settings you can use SHOW (commit d1ecd539477). If there was a strong need for even more than that, we can add something to the grammar. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
