I’m working on a “CANCEL SUBSCRIPTION” feature that has been talked about for rather a long time. (It’s on the bug list: http://www.slony.info/bugzilla
The notion is that if you have a subscription that keeps failing for some reason, we should have a way of dropping the subscription request without being forced to throw away the entire cluster configuration. The special thing about CANCEL SUBSCRIPTION is that it needs to be able to come in and take action against events EARLIER in the event stream than itself.
In analyzing the environment of data available to CANCEL SUBSCRIPTION, it looks like it’s pretty highly constrained. There are quite a number of cases where it should fail to do anything.