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https://issues.apache.org/jira/browse/FLINK-9513?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16531277#comment-16531277
 ] 

ASF GitHub Bot commented on FLINK-9513:
---------------------------------------

Github user StefanRRichter commented on a diff in the pull request:

    https://github.com/apache/flink/pull/6196#discussion_r199783587
  
    --- Diff: 
flink-core/src/main/java/org/apache/flink/api/common/typeutils/CompositeSerializer.java
 ---
    @@ -0,0 +1,275 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * 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.api.common.typeutils;
    +
    +import org.apache.flink.api.java.tuple.Tuple2;
    +import org.apache.flink.core.memory.DataInputView;
    +import org.apache.flink.core.memory.DataOutputView;
    +import org.apache.flink.util.Preconditions;
    +
    +import javax.annotation.Nonnull;
    +
    +import java.io.IOException;
    +import java.util.Arrays;
    +import java.util.List;
    +import java.util.Objects;
    +import java.util.stream.IntStream;
    +
    +/**
    + * Base class for composite serializers.
    + *
    + * <p>This class serializes a composite type using array of its field 
serializers.
    + * Fields are indexed the same way as their serializers.
    + *
    + * @param <T> type of custom serialized value
    + */
    +public abstract class CompositeSerializer<T> extends TypeSerializer<T> {
    +   private static final long serialVersionUID = 1L;
    +
    +   /** Serializers for fields which constitute T. */
    +   protected final TypeSerializer<Object>[] fieldSerializers;
    +
    +   /** Whether T is an immutable type. */
    +   final boolean immutableTargetType;
    +
    +   /** Byte length of target object in serialized form. */
    +   private final int length;
    +
    +   /** Whether any field serializer is stateful. */
    +   private final boolean stateful;
    +
    +   private final int hashCode;
    +
    +   @SuppressWarnings("unchecked")
    +   protected CompositeSerializer(boolean immutableTargetType, 
TypeSerializer<?> ... fieldSerializers) {
    +           Preconditions.checkNotNull(fieldSerializers);
    +           
Preconditions.checkArgument(Arrays.stream(fieldSerializers).allMatch(Objects::nonNull));
    +           this.immutableTargetType = immutableTargetType &&
    +                   
Arrays.stream(fieldSerializers).allMatch(TypeSerializer::isImmutableType);
    +           this.fieldSerializers = (TypeSerializer<Object>[]) 
fieldSerializers;
    +           this.length = calcLength();
    +           this.stateful = isStateful();
    +           this.hashCode = Arrays.hashCode(fieldSerializers);
    +   }
    +
    +   private boolean isStateful() {
    +           TypeSerializer[] duplicatedSerializers = 
duplicateFieldSerializers();
    +           return IntStream.range(0, fieldSerializers.length)
    +                   .anyMatch(i -> fieldSerializers[i] != 
duplicatedSerializers[i]);
    +   }
    +
    +   /** Create new instance from its fields.  */
    +   public abstract T createInstance(@Nonnull Object ... values);
    +
    +   /** Modify field of existing instance. Supported only by mutable types. 
*/
    +   protected abstract void setField(@Nonnull T value, int index, Object 
fieldValue);
    +
    +   /** Get field of existing instance. */
    +   protected abstract Object getField(@Nonnull T value, int index);
    +
    +   /** Factory for concrete serializer. */
    +   protected abstract CompositeSerializer<T> 
createSerializerInstance(TypeSerializer<?> ... originalSerializers);
    +
    +   @Override
    +   public CompositeSerializer<T> duplicate() {
    +           return stateful ? 
createSerializerInstance(duplicateFieldSerializers()) : this;
    --- End diff --
    
    Another small point here for `createSerializerInstance(...)`: we have no 
(non-public) constructor that can also take all boolean flags, length, and 
(maybe) hash directly. So if we copy the serializer, I guess it always goes 
through the whole process again to figure this out, but we could just copy it 
from the previous instance.


> Wrap state binder with TTL logic
> --------------------------------
>
>                 Key: FLINK-9513
>                 URL: https://issues.apache.org/jira/browse/FLINK-9513
>             Project: Flink
>          Issue Type: Sub-task
>          Components: State Backends, Checkpointing
>    Affects Versions: 1.6.0
>            Reporter: Andrey Zagrebin
>            Assignee: Andrey Zagrebin
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.6.0
>
>
> The main idea is to wrap user state value with a class holding the value and 
> the expiration timestamp (maybe meta data in future) and use the new object 
> as a value in the existing implementations:
> {code:java}
> class TtlValue<V> {
>   V value;
>   long expirationTimestamp;
> }
> {code}
> The original state binder factory is wrapped with TtlStateBinder if TTL is 
> enabled:
> {code:java}
> state = ttlConfig.updateType == DISABLED ?
>  bind(binder) : bind(new TtlStateBinder(binder, timerService));
> {code}
> TtlStateBinder decorates the states produced by the original binder with TTL 
> logic wrappers and adds TtlValue serialisation logic:
> {code:java}
> TtlStateBinder {
>     StateBinder binder;
>     ProcessingTimeProvier timeProvider; // System.currentTimeMillis()
>     <V> TtlValueState<V> createValueState(valueDesc) {
>          serializer = new TtlValueSerializer(valueDesc.getSerializer);
>          ttlValueDesc = new ValueDesc(serializer, ...);
>          // or implement custom TypeInfo
>          originalStateWithTtl = binder.createValueState(valueDesc);
>          return new TtlValueState(originalStateWithTtl, timeProvider);
>     }
>       // List, Map, ...
> }
> {code}
> TTL serializer should add expiration timestamp



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