Not OP but I would watch for mutations in the subscribed columns, then test the changed rows on the query's constraints and fire an event if it satisfies them.

Not OP but I would watch for mutations in the subscribed columns, then test the changed rows on the query's constraints and fire an event if it satisfies them. I'm sure there is a more clever/efficient way of doing this though, and I can't wait to see how he/she implements it.