org.apache.flink.runtime.state.StateSnapshotTransformer Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.state;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
import java.util.Optional;
/**
* Transformer of state values which are included or skipped in the snapshot.
*
* This transformer can be applied to state values
* to decide which entries should be included into the snapshot.
* The included entries can be optionally modified before.
*
*
Unless specified differently, the transformer should be applied per entry
* for collection types of state, like list or map.
*
* @param type of state
*/
@FunctionalInterface
@NotThreadSafe
public interface StateSnapshotTransformer {
/**
* Transform or filter out state values which are included or skipped in the snapshot.
*
* @param value non-serialized form of value
* @return value to snapshot or null which means the entry is not included
*/
@Nullable
T filterOrTransform(@Nullable T value);
/** Collection state specific transformer which says how to transform entries of the collection. */
interface CollectionStateSnapshotTransformer extends StateSnapshotTransformer {
enum TransformStrategy {
/** Transform all entries. */
TRANSFORM_ALL,
/**
* Skip first null entries.
*
* While traversing collection entries, as optimisation, stops transforming
* if encounters first non-null included entry and returns it plus the rest untouched.
*/
STOP_ON_FIRST_INCLUDED
}
default TransformStrategy getFilterStrategy() {
return TransformStrategy.TRANSFORM_ALL;
}
}
/**
* This factory creates state transformers depending on the form of values to transform.
*
*
If there is no transforming needed, the factory methods return {@code Optional.empty()}.
*/
interface StateSnapshotTransformFactory {
StateSnapshotTransformFactory NO_TRANSFORM = createNoTransform();
@SuppressWarnings("unchecked")
static StateSnapshotTransformFactory noTransform() {
return (StateSnapshotTransformFactory) NO_TRANSFORM;
}
static StateSnapshotTransformFactory createNoTransform() {
return new StateSnapshotTransformFactory() {
@Override
public Optional> createForDeserializedState() {
return Optional.empty();
}
@Override
public Optional> createForSerializedState() {
return Optional.empty();
}
};
}
Optional> createForDeserializedState();
Optional> createForSerializedState();
}
}