org.apache.flink.runtime.state

Class GenericReducingState<N,T,W extends ValueState<T> & KvState<N>>

java.lang.Object

org.apache.flink.runtime.state.GenericReducingState<N,T,W>

Type Parameters:

N - The type of the namespace.

T - The type of the values stored in this ReducingState.

W - Generic type that extends both the underlying ValueState and KvState.

All Implemented Interfaces:

AppendingState<T,T>, MergingState<T,T>, ReducingState<T>, State, KvState<N>

public class GenericReducingState<N,T,W extends ValueState<T> & KvState<N>>
extends Object
implements ReducingState<T>, KvState<N>

Generic implementation of ReducingState based on a wrapped ValueState.

Constructor Summary

Constructors

Constructor and Description
GenericReducingState(ValueState<T> wrappedState, ReduceFunction<T> reduceFunction) Creates a new ReducingState that wraps the given ValueState.

Method Summary

Modifier and Type	Method and Description
void	add(T value) Updates the operator state accessible by AppendingState.get() by adding the given value to the list of values.
void	clear() Removes the value mapped under the current key.
T	get() Returns the current value for the state.
byte[]	getSerializedValue(byte[] serializedKeyAndNamespace) Returns the serialized value for the given key and namespace.
void	setCurrentNamespace(N namespace) Sets the current namespace, which will be used when using the state access methods.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GenericReducingState

public GenericReducingState(ValueState<T> wrappedState,
                            ReduceFunction<T> reduceFunction)

Creates a new ReducingState that wraps the given ValueState. The ValueState must have a default value of null.

Parameters:

wrappedState - The wrapped ValueState

reduceFunction - The ReduceFunction to use for combining values.

Method Detail

setCurrentNamespace

public void setCurrentNamespace(N namespace)

Description copied from interface: KvState

Sets the current namespace, which will be used when using the state access methods.

Specified by:

setCurrentNamespace in interface KvState<N>

Parameters:

namespace - The namespace.

getSerializedValue

public byte[] getSerializedValue(byte[] serializedKeyAndNamespace)
                          throws Exception

Description copied from interface: KvState

Returns the serialized value for the given key and namespace.

If no value is associated with key and namespace, null is returned.

Specified by:

getSerializedValue in interface KvState<N>

Parameters:

serializedKeyAndNamespace - Serialized key and namespace

Returns:

Serialized value or null if no value is associated with the key and namespace.

Throws:

Exception - Exceptions during serialization are forwarded

get

public T get()
      throws Exception

Description copied from interface: AppendingState

Returns the current value for the state. When the state is not partitioned the returned value is the same for all inputs in a given operator instance. If state partitioning is applied, the value returned depends on the current operator input, as the operator maintains an independent state for each partition.

NOTE TO IMPLEMENTERS: if the state is empty, then this method should return null.

Specified by:

get in interface AppendingState<T,T>

Returns:

The operator state value corresponding to the current input or null if the state is empty.

Throws:

Exception - Thrown if the system cannot access the state.

add

public void add(T value)
         throws Exception

Description copied from interface: AppendingState

Updates the operator state accessible by AppendingState.get() by adding the given value to the list of values. The next time AppendingState.get() is called (for the same state partition) the returned state will represent the updated list.

Specified by:

add in interface AppendingState<T,T>

Parameters:

value - The new value for the state.

Throws:

IOException - Thrown if the system cannot access the state.

Exception

clear

public void clear()

Description copied from interface: State

Removes the value mapped under the current key.

Specified by:

clear in interface State