org.apache.flink.api.common.state

Interface ReducingState<T>

Type Parameters:

T - Type of the value in the operator state

All Superinterfaces:

AppendingState<T,T>, MergingState<T,T>, State

All Known Subinterfaces:

InternalReducingState<K,N,T>

All Known Implementing Classes:

ImmutableReducingState

@PublicEvolving
public interface ReducingState<T>
extends MergingState<T,T>

State interface for reducing state. Elements can be added to the state, they will be combined using a reduce function. The current state can be inspected.

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 consistently together.

Method Summary

Methods inherited from interface org.apache.flink.api.common.state.AppendingState

add, get

Methods inherited from interface org.apache.flink.api.common.state.State

clear