org.apache.flink.api.common.state

Interface StateBackend

@PublicEvolving
public interface StateBackend

The StateBackend is used by StateDescriptor instances to create actual state representations.

Method Summary

Modifier and Type	Method and Description
<T,ACC> FoldingState<T,ACC>	createFoldingState(FoldingStateDescriptor<T,ACC> stateDesc) Creates and returns a new FoldingState.
<T> ListState<T>	createListState(ListStateDescriptor<T> stateDesc) Creates and returns a new ListState.
<T> ReducingState<T>	createReducingState(ReducingStateDescriptor<T> stateDesc) Creates and returns a new ReducingState.
<T> ValueState<T>	createValueState(ValueStateDescriptor<T> stateDesc) Creates and returns a new ValueState.

Method Detail

createValueState

<T> ValueState<T> createValueState(ValueStateDescriptor<T> stateDesc)
                            throws Exception

Creates and returns a new ValueState.

Type Parameters:

T - The type of the value that the ValueState can store.

Parameters:

stateDesc - The StateDescriptor that contains the name of the state.

Throws:

Exception

createListState

<T> ListState<T> createListState(ListStateDescriptor<T> stateDesc)
                          throws Exception

Creates and returns a new ListState.

Type Parameters:

T - The type of the values that the ListState can store.

Parameters:

stateDesc - The StateDescriptor that contains the name of the state.

Throws:

Exception

createReducingState

<T> ReducingState<T> createReducingState(ReducingStateDescriptor<T> stateDesc)
                                  throws Exception

Creates and returns a new ReducingState.

Type Parameters:

T - The type of the values that the ListState can store.

Parameters:

stateDesc - The StateDescriptor that contains the name of the state.

Throws:

Exception

createFoldingState

<T,ACC> FoldingState<T,ACC> createFoldingState(FoldingStateDescriptor<T,ACC> stateDesc)
                                        throws Exception

Creates and returns a new FoldingState.

Type Parameters:

T - Type of the values folded into the state

ACC - Type of the value in the state

Parameters:

stateDesc - The StateDescriptor that contains the name of the state.

Throws:

Exception