[SPARK-5840][SQL] HiveContext cannot be serialized due to tuple extraction

Also added test cases for checking the serializability of HiveContext and SQLContext.

Author: Reynold Xin <rxin@databricks.com>

Closes #4628 from rxin/SPARK-5840 and squashes the following commits:

ecb3bcd [Reynold Xin] test cases and reviews.
55eb822 [Reynold Xin] [SPARK-5840][SQL] HiveContext cannot be serialized due to tuple extraction.

sql/core/src/test/scala/org/apache/spark/sql/SerializationSuite.scala

@@ -0,0 +1,32 @@
+/*
+ * 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.spark.sql
+
+import org.scalatest.FunSuite
+
+import org.apache.spark.SparkConf
+import org.apache.spark.serializer.JavaSerializer
+import org.apache.spark.sql.test.TestSQLContext
+
+class SerializationSuite extends FunSuite {
+
+  test("[SPARK-5235] SQLContext should be serializable") {
+    val sqlContext = new SQLContext(TestSQLContext.sparkContext)
+    new JavaSerializer(new SparkConf()).newInstance().serialize(sqlContext)
+  }
+}

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

@@ -222,22 +222,25 @@ class HiveContext(sc: SparkContext) extends SQLContext(sc) {
    *    SQLConf.  Additionally, any properties set by set() or a SET command inside sql() will be
    *    set in the SQLConf *as well as* in the HiveConf.
    */
-  @transient protected[hive] lazy val (hiveconf, sessionState) =
-    Option(SessionState.get())
-      .orElse {
-        val newState = new SessionState(new HiveConf(classOf[SessionState]))
-        // Only starts newly created `SessionState` instance.  Any existing `SessionState` instance
-        // returned by `SessionState.get()` must be the most recently started one.
-        SessionState.start(newState)
-        Some(newState)
+  @transient protected[hive] lazy val sessionState: SessionState = {
+    var state = SessionState.get()
+    if (state == null) {
+      state = new SessionState(new HiveConf(classOf[SessionState]))
+      SessionState.start(state)
     }
-      .map { state =>
-        setConf(state.getConf.getAllProperties)
-        if (state.out == null) state.out = new PrintStream(outputBuffer, true, "UTF-8")
-        if (state.err == null) state.err = new PrintStream(outputBuffer, true, "UTF-8")
-        (state.getConf, state)
+    if (state.out == null) {
+      state.out = new PrintStream(outputBuffer, true, "UTF-8")
+    }
+    if (state.err == null) {
+      state.err = new PrintStream(outputBuffer, true, "UTF-8")
+    }
+    state
+  }
+
+  @transient protected[hive] lazy val hiveconf: HiveConf = {
+    setConf(sessionState.getConf.getAllProperties)
+    sessionState.getConf
   }
-      .get
 
   override def setConf(key: String, value: String): Unit = {
     super.setConf(key, value)

sql/hive/src/test/scala/org/apache/spark/sql/hive/SerializationSuite.scala

@@ -0,0 +1,33 @@
+/*
+ * 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.spark.sql.hive
+
+import org.scalatest.FunSuite
+
+import org.apache.spark.SparkConf
+import org.apache.spark.serializer.JavaSerializer
+import org.apache.spark.sql.hive.test.TestHive
+
+class SerializationSuite extends FunSuite {
+
+  test("[SPARK-5840] HiveContext should be serializable") {
+    val hiveContext = new HiveContext(TestHive.sparkContext)
+    hiveContext.hiveconf
+    new JavaSerializer(new SparkConf()).newInstance().serialize(hiveContext)
+  }
+}