> How good will that be in performance.
In my experience, not great. It's definitely better than not having it at all, but it does not make for quick queries and caused serious connection overhead when a query referenced that foreign table. I've since moved to logical replication to improve the situation there.
In SQL Server I had never noticed the difference when I had to do cross-db queries. There may or may not be a difference, but it was never something that I had to think about or look up, so I am not sure.
It's something I do still miss though, as it sure was convenient.
Just my $0.02.
-Adam