org.apache.flink.api.common.state

Interface ListState<T>

Type Parameters:

T - Type of values that this list state keeps.

All Superinterfaces:

AppendingState<T,Iterable<T>>, MergingState<T,Iterable<T>>, State

All Known Subinterfaces:

InternalListState<K,N,T>

All Known Implementing Classes:

ImmutableListState, PartitionableListState, SimpleVersionedListState

@PublicEvolving
public interface ListState<T>
extends MergingState<T,Iterable<T>>

State interface for partitioned list state in Operations. The state is accessed and modified by user functions, and checkpointed consistently by the system as part of the distributed snapshots.

The state can be a keyed list state or an operator list state.

When it is a keyed list state, it is accessed by functions applied on a KeyedStream. The key is automatically supplied by the system, so the function always sees the value mapped to the key of the current element. That way, the system can handle stream and state partitioning consistently together.

When it is an operator list state, the list is a collection of state items that are independent from each other and eligible for redistribution across operator instances in case of changed operator parallelism.

Method Summary

Modifier and Type	Method and Description
void	addAll(List<T> values) Updates the operator state accessible by AppendingState.get() by adding the given values to existing list of values.
void	update(List<T> values) Updates the operator state accessible by AppendingState.get() by updating existing values to the given list of values.

Methods inherited from interface org.apache.flink.api.common.state.AppendingState

add, get

Methods inherited from interface org.apache.flink.api.common.state.State

clear

Method Detail

update

void update(List<T> values)
     throws Exception

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

If an empty list is passed in, the state value will be null.

Null value passed in or any null value in list is not allowed.

Parameters:

values - The new values for the state.

Throws:

Exception - The method may forward exception thrown internally (by I/O or functions, or sanity check for null value).

addAll

void addAll(List<T> values)
     throws Exception

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

If an empty list is passed in, the state value remains unchanged.

Null value passed in or any null value in list is not allowed.

Parameters:

values - The new values to be added to the state.

Throws:

Exception - The method may forward exception thrown internally (by I/O or functions, or sanity check for null value).