org.apache.flink.runtime.state

Interface StateTransformationFunction<S,T>

Type Parameters:

S - type of the previous state that is the bases for the computation of the new state.

T - type of the element value that is used to compute the change of state.

@Internal
public interface StateTransformationFunction<S,T>

Interface for a binary function that is used for push-down of state transformation into state backends. The function takes as inputs the old state and an element. From those inputs, the function computes the new state.

Method Summary

Modifier and Type	Method and Description
S	apply(S previousState, T value) Binary function that applies a given value to the given old state to compute the new state.

Method Detail

apply

S apply(S previousState,
        T value)
 throws Exception

Binary function that applies a given value to the given old state to compute the new state.

Parameters:

previousState - the previous state that is the basis for the transformation.

value - the value that the implementation applies to the old state to obtain the new state.

Returns:

the new state, computed by applying the given value on the given old state.

Throws:

Exception - if something goes wrong in applying the transformation function.