Github user liancheng commented on a diff in the pull request: https://github.com/apache/spark/pull/3640#discussion_r21512352 --- Diff: sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUdfs.scala --- @@ -54,47 +54,95 @@ private[hive] abstract class HiveFunctionRegistry val functionClassName = functionInfo.getFunctionClass.getName if (classOf[UDF].isAssignableFrom(functionInfo.getFunctionClass)) { - HiveSimpleUdf(functionClassName, children) + HiveSimpleUdf(new HiveFunctionCache(functionClassName), children) } else if (classOf[GenericUDF].isAssignableFrom(functionInfo.getFunctionClass)) { - HiveGenericUdf(functionClassName, children) + HiveGenericUdf(new HiveFunctionCache(functionClassName), children) } else if ( classOf[AbstractGenericUDAFResolver].isAssignableFrom(functionInfo.getFunctionClass)) { - HiveGenericUdaf(functionClassName, children) + HiveGenericUdaf(new HiveFunctionCache(functionClassName), children) } else if (classOf[UDAF].isAssignableFrom(functionInfo.getFunctionClass)) { - HiveUdaf(functionClassName, children) + HiveUdaf(new HiveFunctionCache(functionClassName), children) } else if (classOf[GenericUDTF].isAssignableFrom(functionInfo.getFunctionClass)) { - HiveGenericUdtf(functionClassName, Nil, children) + HiveGenericUdtf(new HiveFunctionCache(functionClassName), Nil, children) } else { sys.error(s"No handler for udf ${functionInfo.getFunctionClass}") } } } -private[hive] trait HiveFunctionFactory { - val functionClassName: String - - def createFunction[UDFType]() = - getContextOrSparkClassLoader.loadClass(functionClassName).newInstance.asInstanceOf[UDFType] -} - -private[hive] abstract class HiveUdf extends Expression with Logging with HiveFunctionFactory { - self: Product => +/** + * This class provides the UDF creation and also the UDF instance serialization and + * de-serialization cross process boundary. + * + * We use class instead of trait, seems property variables of trait cannot be serialized when + * bundled with Case Class; in the other hand, we need to intercept the UDF instance ser/de. + * the "Has-a" probably better than "Is-a". + * @param functionClassName UDF class name + */ +class HiveFunctionCache(var functionClassName: String) extends java.io.Externalizable { + // for Serialization + def this() = this(null) + + private var instance: Any = null + + def writeExternal(out: java.io.ObjectOutput) { + // output the function name + out.writeUTF(functionClassName) + + // Write a flag if instance is null or not + out.writeBoolean(instance != null) --- End diff -- Does this relate to the `HiveSimpleUdf` and UDF bridge case you mentioned offline? Would be better to leave a comment here. I was confused when reading this.
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