Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/6196#discussion_r199782860
--- 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();
--- End diff --
The flag for `isStateful()` is the only one that I suggested as a candidate
for lazy init when `duplicate()` is called for the first time. Reason is that
duplicating some types of inner serializers can sometimes be a bit expensive.
But again, I feel that this can also be changed in followup work, if needed.
---
