[GitHub] klion26 commented on a change in pull request #7734: [FLINK-11334][core] Migrate EnumValueSerializer to use new serialization compatibility abstractions

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klion26 commented on a change in pull request #7734: [FLINK-11334][core] Migrate EnumValueSerializer to use new serialization compatibility abstractions
URL: https://github.com/apache/flink/pull/7734#discussion_r258052203
 
 

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 File path: flink-scala/src/main/scala/org/apache/flink/api/scala/typeutils/ScalaEnumSerializerSnapshot.scala
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 @@ -0,0 +1,136 @@
+/*
+ * 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.scala.typeutils
+
+import java.io.IOException
+
+import org.apache.flink.api.common.typeutils.{TypeSerializer, TypeSerializerSchemaCompatibility, TypeSerializerSnapshot}
+import org.apache.flink.api.java.typeutils.runtime.{DataInputViewStream, DataOutputViewStream}
+import org.apache.flink.core.memory.{DataInputView, DataOutputView}
+import org.apache.flink.util.{InstantiationUtil, Preconditions}
+
+import scala.collection.mutable.ListBuffer
+
+class ScalaEnumSerializerSnapshot[E <: Enumeration]
+  extends TypeSerializerSnapshot[E#Value] {
+
+  var enumClass: Class[E] = _
+  var previousEnumConstants: List[(String, Int)] = _
+
+  def this(enum: E) = {
+    this()
+    this.enumClass = Preconditions.checkNotNull(enum).getClass.asInstanceOf[Class[E]]
+    this.previousEnumConstants = enum.values.toList.map(x => (x.toString, x.id))
+  }
+
+  def this(enumClass: Class[E], previousEnumConstants: List[(String, Int)]) = {
+    this()
+    this.enumClass = Preconditions.checkNotNull(enumClass)
+    this.previousEnumConstants = Preconditions.checkNotNull(previousEnumConstants)
+  }
+
+  override def getCurrentVersion: Int = ScalaEnumSerializerSnapshot.VERSION
+
+  override def writeSnapshot(out: DataOutputView): Unit = {
+    val outViewWrapper = new DataOutputViewStream(out)
+    try {
+      out.writeUTF(enumClass.getName)
+
+      out.writeInt(previousEnumConstants.length)
+      for ((name, idx) <- previousEnumConstants) {
+        out.writeUTF(name)
+        out.writeInt(idx)
+      }
+    } finally if (outViewWrapper != null) outViewWrapper.close()
+  }
+
+  override def readSnapshot(
+    readVersion: Int, in: DataInputView, userCodeClassLoader: ClassLoader): Unit = {
+    val inViewWrapper = new DataInputViewStream(in)
+    try {
+      if (readVersion == 1) {
+        enumClass = InstantiationUtil.deserializeObject(
+          inViewWrapper, userCodeClassLoader)
+
+        // read null from input stream
+        InstantiationUtil.deserializeObject(inViewWrapper, userCodeClassLoader)
+        previousEnumConstants = List()
+      } else if (readVersion >= 2) {
+        enumClass = Class.forName(
+          in.readUTF(), true, userCodeClassLoader).asInstanceOf[Class[E]]
+
+        val length = in.readInt()
+        val listBuffer = ListBuffer[(String, Int)]()
+
+        for (_ <- 0 until length) {
+          val name = in.readUTF()
+          val idx = in.readInt()
+          listBuffer += ((name, idx))
+        }
+
+        previousEnumConstants = listBuffer.toList
+      } else {
+        throw new IOException(
+          s"Cannot deserialize ${getClass.getSimpleName} with version $readVersion.")
+      }
+    } catch {
+      case e: ClassNotFoundException =>
+        throw new IOException("The requested enum class cannot be found in classpath.", e)
+    }
+    finally if (inViewWrapper != null) inViewWrapper.close()
+  }
+
+  override def restoreSerializer(): TypeSerializer[E#Value] = {
+    enumClass.newInstance().asInstanceOf[TypeSerializer[E#Value]]
+  }
+
+  override def resolveSchemaCompatibility(
+    newSerializer: TypeSerializer[E#Value]): TypeSerializerSchemaCompatibility[E#Value] = {
+    newSerializer match {
+      case newEnumSerializer: EnumValueSerializer[_] => {
+        if (enumClass.equals(newEnumSerializer.enum.getClass)) {
+          for ((previousEnumConstant, idx) <- previousEnumConstants) {
+            val enumValue = try {
+              newEnumSerializer.enum(idx)
+            } catch {
+              case _: NoSuchElementException =>
+                // couldn't find an enum value for the given index
+                return TypeSerializerSchemaCompatibility.incompatible()
+            }
+
+            if (!previousEnumConstant.equals(enumValue.toString)) {
+              // compatible only if new enum constants are only appended,
+              // and original constants must be in the exact same order
+              return TypeSerializerSchemaCompatibility.compatibleAfterMigration()
 
 Review comment:
   If the index of the value actually changed, there should be incompatible, I'll update it. because in `EnumValueSerializer#serializer` we use `Enumeration#Value.id`

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