IN- Type of the value added to the state.
OUT- Type of the value extracted from the state.
@PublicEvolving public interface AggregatingState<IN,OUT> extends MergingState<IN,OUT>
Stateinterface for aggregating state, based on an
AggregateFunction. Elements that are added to this type of state will be eagerly pre-aggregated using a given
The state holds internally always the accumulator type of the
When accessing the result of the state, the function's
The state is accessed and modified by user functions, and checkpointed consistently by the system as part of the distributed snapshots.
The state is only accessible by functions applied on a
KeyedStream. The key is
automatically supplied by the system, so the function always sees the value mapped to the
key of the current element. That way, the system can handle stream and state partitioning
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