avoid Simple UDF to be serialized

Author: chenghao-intel

sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUdfs.scala

@@ -86,39 +86,50 @@ class HiveFunctionCache(var functionClassName: String) extends java.io.Externali
   private var instance: Any = null
 
   def writeExternal(out: java.io.ObjectOutput) {
-    // Some of the UDF are serializable, but some others are not
-    // Hive Utilities can handle both cases
-    val baos = new java.io.ByteArrayOutputStream()
-    HiveShim.serializePlan(instance, baos)
-    val functionInBytes = baos.toByteArray
-
     // output the function name
     out.writeUTF(functionClassName)
 
-    // output the function bytes
-    out.writeInt(functionInBytes.length)
-    out.write(functionInBytes, 0, functionInBytes.length)
+    // Write a flag if instance is null or not
+    out.writeBoolean(instance != null)
+    if (instance != null) {
+      // Some of the UDF are serializable, but some others are not
+      // Hive Utilities can handle both cases
+      val baos = new java.io.ByteArrayOutputStream()
+      HiveShim.serializePlan(instance, baos)
+      val functionInBytes = baos.toByteArray
+
+      // output the function bytes
+      out.writeInt(functionInBytes.length)
+      out.write(functionInBytes, 0, functionInBytes.length)
+    }
   }
 
   def readExternal(in: java.io.ObjectInput) {
     // read the function name
     functionClassName = in.readUTF()
 
-    // read the function in bytes
-    val functionInBytesLength = in.readInt()
-    val functionInBytes = new Array[Byte](functionInBytesLength)
-    in.read(functionInBytes, 0, functionInBytesLength)
+    if (in.readBoolean()) {
+      // if the instance is not null
+      // read the function in bytes
+      val functionInBytesLength = in.readInt()
+      val functionInBytes = new Array[Byte](functionInBytesLength)
+      in.read(functionInBytes, 0, functionInBytesLength)
 
-    // deserialize the function object via Hive Utilities
-    instance = HiveShim.deserializePlan(new java.io.ByteArrayInputStream(functionInBytes),
-      getContextOrSparkClassLoader.loadClass(functionClassName))
+      // deserialize the function object via Hive Utilities
+      instance = HiveShim.deserializePlan(new java.io.ByteArrayInputStream(functionInBytes),
+        getContextOrSparkClassLoader.loadClass(functionClassName))
+    }
   }
 
-  def createFunction[UDFType]() = {
-    if (instance == null) {
-      instance = getContextOrSparkClassLoader.loadClass(functionClassName).newInstance
+  def createFunction[UDFType](alwaysCreateNewInstance: Boolean = false) = {
+    if (alwaysCreateNewInstance) {
+      getContextOrSparkClassLoader.loadClass(functionClassName).newInstance.asInstanceOf[UDFType]
+    } else {
+      if (instance == null) {
+        instance = getContextOrSparkClassLoader.loadClass(functionClassName).newInstance
+      }
+      instance.asInstanceOf[UDFType]
     }
-    instance.asInstanceOf[UDFType]
   }
 }
 
@@ -130,7 +141,7 @@ private[hive] case class HiveSimpleUdf(cache: HiveFunctionCache, children: Seq[E
   def nullable = true
 
   @transient
-  lazy val function = cache.createFunction[UDFType]()
+  lazy val function = cache.createFunction[UDFType](true) // Simple UDF should be not serialized.
 
   @transient
   protected lazy val method =