Group-window aggregates for streaming tables are currently not done in an incremental fashion. This means that the window collects all records and performs the aggregation when the window is closed instead of eagerly updating a partial aggregate for every added record. Since records are buffered, non-incremental aggregation requires more storage space than incremental aggregation.
The DataStream API which is used under the hood of the streaming Table API features incremental aggregation using a ReduceFunction.
We should add support for incremental aggregation in group-windows.
This is a follow-up task of