Yeah you can subscribe to overall changes to the data on a row by row basis but can't subscribe to an actual query. Many apps and libraries imitate reactive queries by just refetching all queries from Postgres when any data changes or just repeatedly polling the query every 10 seconds or so but this puts a lot of strain on the database. You can just subscribe to the replication stream but then you're left trying to reconstruct your queries in your application code which is extremely error prone and painful
