The TableAggregateFunction javadocs indicate that either "emitValue" or "emitUpdateWithRetract" is required.
But if I implement my TableAggregateFunction with "emitUpdateWithRetract", I get a validation error. If I implement both methods it works, but emitUpdateWithRetract is not used. Peering into the Flink source code, I see that ImperativeAggCodeGen validates the presence of emitValue, but is agnostic to emitUpdateWithRetract. More curiously, Flink's source code doesn't have a single test with a TableAggregateFunction that uses emitUpdateWithRetract. Is this a ghost feature? Thanks, Adam
