org.apache.flink.runtime.state

Interface KeyedStateBackend<K>

Type Parameters:

K - The key by which state is keyed.

All Superinterfaces:

Disposable, InternalKeyContext<K>

All Known Implementing Classes:

AbstractKeyedStateBackend, HeapKeyedStateBackend, RocksDBKeyedStateBackend

public interface KeyedStateBackend<K>
extends InternalKeyContext<K>, Disposable

A keyed state backend provides methods for managing keyed state.

Method Summary

Modifier and Type	Method and Description
<N,S extends State,T> void	applyToAllKeys(N namespace, TypeSerializer<N> namespaceSerializer, StateDescriptor<S,T> stateDescriptor, KeyedStateFunction<K,S> function) Applies the provided KeyedStateFunction to the state with the provided StateDescriptor of all the currently active keys.
void	dispose() Disposes the object and releases all resources.
<N> java.util.stream.Stream<K>	getKeys(String state, N namespace)
<N,S extends State,T> S	getOrCreateKeyedState(TypeSerializer<N> namespaceSerializer, StateDescriptor<S,T> stateDescriptor) Creates or retrieves a keyed state backed by this state backend.
<N,S extends State> S	getPartitionedState(N namespace, TypeSerializer<N> namespaceSerializer, StateDescriptor<S,?> stateDescriptor) Creates or retrieves a partitioned state backed by this state backend.
void	setCurrentKey(K newKey) Sets the current key that is used for partitioned state.

Methods inherited from interface org.apache.flink.runtime.state.heap.InternalKeyContext

getCurrentKey, getCurrentKeyGroupIndex, getKeyGroupRange, getKeySerializer, getNumberOfKeyGroups

Method Detail

setCurrentKey

void setCurrentKey(K newKey)

Sets the current key that is used for partitioned state.

Parameters:

newKey - The new current key.

applyToAllKeys

<N,S extends State,T> void applyToAllKeys(N namespace,
                                          TypeSerializer<N> namespaceSerializer,
                                          StateDescriptor<S,T> stateDescriptor,
                                          KeyedStateFunction<K,S> function)
                                   throws Exception

Applies the provided KeyedStateFunction to the state with the provided StateDescriptor of all the currently active keys.

Type Parameters:

N - The type of the namespace.

S - The type of the state.

Parameters:

namespace - the namespace of the state.

namespaceSerializer - the serializer for the namespace.

stateDescriptor - the descriptor of the state to which the function is going to be applied.

function - the function to be applied to the keyed state.

Throws:

Exception

getKeys

<N> java.util.stream.Stream<K> getKeys(String state,
                                       N namespace)

Parameters:

state - State variable for which existing keys will be returned.

namespace - Namespace for which existing keys will be returned.

Returns:

A stream of all keys for the given state and namespace. Modifications to the state during iterating over it keys are not supported.

getOrCreateKeyedState

<N,S extends State,T> S getOrCreateKeyedState(TypeSerializer<N> namespaceSerializer,
                                              StateDescriptor<S,T> stateDescriptor)
                                       throws Exception

Creates or retrieves a keyed state backed by this state backend.

Type Parameters:

N - The type of the namespace.

S - The type of the state.

Parameters:

namespaceSerializer - The serializer used for the namespace type of the state

stateDescriptor - The identifier for the state. This contains name and can create a default state value.

Returns:

A new key/value state backed by this backend.

Throws:

Exception - Exceptions may occur during initialization of the state and should be forwarded.

getPartitionedState

<N,S extends State> S getPartitionedState(N namespace,
                                          TypeSerializer<N> namespaceSerializer,
                                          StateDescriptor<S,?> stateDescriptor)
                                   throws Exception

Creates or retrieves a partitioned state backed by this state backend. TODO: NOTE: This method does a lot of work caching / retrieving states just to update the namespace. This method should be removed for the sake of namespaces being lazily fetched from the keyed state backend, or being set on the state directly.

Type Parameters:

N - The type of the namespace.

S - The type of the state.

Parameters:

stateDescriptor - The identifier for the state. This contains name and can create a default state value.

Returns:

A new key/value state backed by this backend.

Throws:

Exception - Exceptions may occur during initialization of the state and should be forwarded.

dispose

void dispose()

Description copied from interface: Disposable

Disposes the object and releases all resources. After calling this method, calling any methods on the object may result in undefined behavior.

Specified by:

dispose in interface Disposable