org.apache.flink.runtime.state

Interface KeyedStateBackend<K>

Type Parameters:

K - The key by which state is keyed.

All Superinterfaces:

Disposable, KeyedStateFactory, PriorityQueueSetFactory

All Known Subinterfaces:

CheckpointableKeyedStateBackend<K>, TestableKeyedStateBackend<K>

All Known Implementing Classes:

AbstractKeyedStateBackend, BatchExecutionKeyedStateBackend, ChangelogKeyedStateBackend, HeapKeyedStateBackend, RocksDBKeyedStateBackend

public interface KeyedStateBackend<K>
extends KeyedStateFactory, PriorityQueueSetFactory, Disposable

A keyed state backend provides methods for managing keyed state.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	KeyedStateBackend.KeySelectionListener<K> Listener is given a callback when setCurrentKey(K) is called (key context changes).

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.
boolean	deregisterKeySelectionListener(KeyedStateBackend.KeySelectionListener<K> listener) Stop calling listener registered in registerKeySelectionListener(org.apache.flink.runtime.state.KeyedStateBackend.KeySelectionListener<K>).
void	dispose() Disposes the object and releases all resources.
K	getCurrentKey()
<N> java.util.stream.Stream<K>	getKeys(String state, N namespace)
<N> java.util.stream.Stream<Tuple2<K,N>>	getKeysAndNamespaces(String state)
TypeSerializer<K>	getKeySerializer()
<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.
default boolean	isSafeToReuseKVState() Whether it's safe to reuse key-values from the state-backend, e.g for the purpose of optimization.
default boolean	isStateImmutableInStateBackend(CheckpointType checkpointOptions) Deprecated.
void	registerKeySelectionListener(KeyedStateBackend.KeySelectionListener<K> listener) State backend will call KeyedStateBackend.KeySelectionListener.keySelected(K) when key context is switched if supported.
void	setCurrentKey(K newKey) Sets the current key that is used for partitioned state.

Methods inherited from interface org.apache.flink.runtime.state.KeyedStateFactory

createOrUpdateInternalState, createOrUpdateInternalState, createOrUpdateInternalState

Methods inherited from interface org.apache.flink.runtime.state.PriorityQueueSetFactory

create, create

Method Detail

setCurrentKey

void setCurrentKey(K newKey)

Sets the current key that is used for partitioned state.

Parameters:

newKey - The new current key.

getCurrentKey

K getCurrentKey()

Returns:

Current key.

getKeySerializer

TypeSerializer<K> getKeySerializer()

Returns:

Serializer of the 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.

getKeysAndNamespaces

<N> java.util.stream.Stream<Tuple2<K,N>> getKeysAndNamespaces(String state)

Parameters:

state - State variable 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. Implementations go not make any ordering guarantees about the returned tupes. Two records with the same key or namespace may not be returned near each other in the stream.

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

registerKeySelectionListener

void registerKeySelectionListener(KeyedStateBackend.KeySelectionListener<K> listener)

State backend will call KeyedStateBackend.KeySelectionListener.keySelected(K) when key context is switched if supported.

deregisterKeySelectionListener

boolean deregisterKeySelectionListener(KeyedStateBackend.KeySelectionListener<K> listener)

Stop calling listener registered in registerKeySelectionListener(org.apache.flink.runtime.state.KeyedStateBackend.KeySelectionListener<K>).

Returns:

returns true iff listener was registered before.

isStateImmutableInStateBackend

@Deprecated
default boolean isStateImmutableInStateBackend(CheckpointType checkpointOptions)

Deprecated.

isSafeToReuseKVState

default boolean isSafeToReuseKVState()

Whether it's safe to reuse key-values from the state-backend, e.g for the purpose of optimization.

NOTE: this method should not be used to check for InternalPriorityQueue, as the priority queue could be stored on different locations, e.g RocksDB state-backend could store that on JVM heap if configuring HEAP as the time-service factory.

Returns:

returns ture if safe to reuse the key-values from the state-backend.