[GitHub] tzulitai commented on a change in pull request #6881: [FLINK-10605] [core] Upgrade AvroSerializer snapshot to implement new TypeSerializerSnapshot interface

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tzulitai commented on a change in pull request #6881: [FLINK-10605] [core] Upgrade AvroSerializer snapshot to implement new TypeSerializerSnapshot interface
URL: https://github.com/apache/flink/pull/6881#discussion_r226600689
 
 

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 File path: flink-formats/flink-avro/src/main/java/org/apache/flink/formats/avro/typeutils/AvroSerializerSnapshot.java
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+/*
+ * 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.formats.avro.typeutils;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.api.common.typeutils.TypeSerializerSchemaCompatibility;
+import org.apache.flink.api.common.typeutils.TypeSerializerSnapshot;
+import org.apache.flink.core.memory.DataInputView;
+import org.apache.flink.core.memory.DataOutputView;
+
+import org.apache.avro.Schema;
+import org.apache.avro.SchemaCompatibility;
+import org.apache.avro.SchemaCompatibility.SchemaPairCompatibility;
+
+import java.io.IOException;
+import java.util.Objects;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * An {@code Avro} specific implementation of a {@link TypeSerializerSnapshot}.
+ *
+ * @param <T> The data type that the originating serializer of this configuration serializes.
+ */
+public final class AvroSerializerSnapshot<T> implements TypeSerializerSnapshot<T> {
+	private Class<T> runtimeType;
+	private Schema schema;
+
+	@SuppressWarnings("WeakerAccess")
+	public AvroSerializerSnapshot() {
+		// this constructor is used when restoring from a checkpoint.
+	}
+
+	AvroSerializerSnapshot(Schema schema, Class<T> runtimeType) {
+		this.schema = schema;
+		this.runtimeType = runtimeType;
+	}
+
+	@Override
+	public int getCurrentVersion() {
+		return 1;
+	}
+
+	@Override
+	public void write(DataOutputView out) throws IOException {
+		checkNotNull(runtimeType);
+		checkNotNull(schema);
+
+		out.writeUTF(runtimeType.getName());
+		out.writeUTF(schema.toString(false));
+	}
+
+	@Override
+	public void read(int readVersion, DataInputView in, ClassLoader userCodeClassLoader) throws IOException {
+		final String previousRuntimeClassName = in.readUTF();
+		final String previousSchemaDefinition = in.readUTF();
+
+		this.runtimeType = findClassOrThrow(userCodeClassLoader, previousRuntimeClassName);
+		this.schema = parseAvroSchema(previousSchemaDefinition);
+	}
+
+	@Override
+	public <NS extends TypeSerializer<T>> TypeSerializerSchemaCompatibility<T, NS>
+	resolveSchemaCompatibility(NS newSerializer) {
+		if (!(newSerializer instanceof AvroSerializer)) {
+			return TypeSerializerSchemaCompatibility.incompatible();
+		}
+		AvroSerializer<?> newAvroSerializer = (AvroSerializer<?>) newSerializer;
+		return resolveSchemaCompatibility(schema, newAvroSerializer.getAvroSchema());
+	}
+
+	@Override
+	public TypeSerializer<T> restoreSerializer() {
+		checkNotNull(runtimeType);
+		checkNotNull(schema);
+
+		if (AvroSerializer.isGenericRecord(runtimeType)) {
+			return new AvroSerializer<>(runtimeType, schema);
+		}
+		else {
+			return new AvroSerializer<>(runtimeType);
 
 Review comment:
   I think regardless of whether the type is Avro or specific, the `restoreSerializer` should always instantiate an AvroSerializer with the snapshotted schema.
   
   With `new AvroSerializer<>(runtimeType);`, the schema used, as far as I understand Avro, will be the new one attached to the generated Specific record.

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