Hi Ning,Answer you question:And why is rich functions not allowed here?If you need access to the state API, you can consider using ProcessWindowFunction, which allows you to use ProcessWindowFunction.Thanks, vino.Ning Shi <ningshi2@xxxxxxxxx> 于2018年9月10日周一 上午11:28写道：Since the aggregate() function on a keyed window stream does not allow
using rich functions, I can only use an AggregateFunction. Is the
accumulator state of the AggregateFunction backed by RocksDB and
persisted in checkpoints if I use the RocksDB backend. My job looks
like the following,
Since the stream has high cardinality keys, each window could have
millions of them. If the accumulator state is not backed by RocksDB,
there might be a lot of data stored on the heap.
And why is rich functions not allowed here?