Hi, While testing a patch today, I tried to set up logical replication on the same cluster. Although I have done that many times before, I made a mistake this time: I accidentally ran the CREATE SUBSCRIPTION command in the source database session, and the subscription was created successfully: ``` evantest=# CREATE SUBSCRIPTION mysub CONNECTION 'host=localhost dbname=evantest user=repl password=secret' PUBLICATION mypub WITH (create_slot = false); CREATE SUBSCRIPTION ```
After that, something weird started to happen. The destination table was empty, but the logs kept reporting duplicate-key errors. It took me a while to realize that the problem was this mistake. This made me wonder whether we should block this kind of loopback logical replication to the same database. I am not aware of a way to use different destination table names, so this setup does not seem useful. Blocking it could help prevent this kind of unnecessary mistake. Before working on a patch, I wanted to check with hackers first. If there are no objections, I can propose a patch. Please let me know if I am missing something. Best regards, -- Chao Li (Evan) HighGo Software Co., Ltd. https://www.highgo.com/
