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https://issues.apache.org/jira/browse/FLINK-6096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15942994#comment-15942994
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ASF GitHub Bot commented on FLINK-6096:
---------------------------------------
Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/3558#discussion_r107908422
--- Diff:
flink-runtime/src/main/java/org/apache/flink/migration/MigrationInstantiationUtil.java
---
@@ -0,0 +1,114 @@
+/*
+ * 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.migration;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.migration.v0.SavepointV0;
+import org.apache.flink.util.InstantiationUtil;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectStreamClass;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Utility class to deserialize legacy classes for migration.
+ */
+@PublicEvolving
+public final class MigrationInstantiationUtil {
+
+ private static final Map<Integer, Map<String, String>>
MigrationMappings = new HashMap<Integer, Map<String, String>>() {{
--- End diff --
Minor code style comment: we use upper case and underscore for the names of
all static final variables in Flink. For example: MIGRATION_MAPPINGS.
> Refactor the migration of old versioned savepoints
> --------------------------------------------------
>
> Key: FLINK-6096
> URL: https://issues.apache.org/jira/browse/FLINK-6096
> Project: Flink
> Issue Type: Improvement
> Components: State Backends, Checkpointing
> Reporter: Xiaogang Shi
> Assignee: Xiaogang Shi
>
> Existing code for the migration of old-versioned savepoints does not allow to
> correctly deserialize those classes changed in different versions. I think
> we should create a migration package for each old-versioned savepoint and put
> all migrated classes in the savepoint there. A mapping can be deployed to
> record those migrated classes in the savepoint so that we can correctly
> deserialize them.
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