org.apache.flink.runtime.state.StateTransformationFunction Maven / Gradle / Ivy
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.flink.runtime.state;
import org.apache.flink.annotation.Internal;
/**
* 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.
*
* @param type of the previous state that is the bases for the computation of the new state.
* @param type of the element value that is used to compute the change of state.
*/
@Internal
public interface StateTransformationFunction {
/**
* Binary function that applies a given value to the given old state to compute the new state.
*
* @param previousState the previous state that is the basis for the transformation.
* @param value the value that the implementation applies to the old state to obtain the new state.
* @return 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.
*/
S apply(S previousState, T value) throws Exception;
}