Port HIVE-10646

Author: wangyum

sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/SparkThriftServerProtocolVersionsSuite.scala

@@ -245,8 +245,7 @@ class SparkThriftServerProtocolVersionsSuite extends HiveThriftJdbcTest {
       }
     }
 
-    // TODO: enable this test case after port HIVE-10646
-    ignore(s"$version get void") {
+    test(s"$version get void") {
       testExecuteStatementWithProtocolVersion(version, "SELECT null") { rs =>
         assert(rs.next())
         assert(rs.getString(1) === null)

sql/hive-thriftserver/v1.2.1/src/main/java/org/apache/hive/service/cli/ColumnValue.java

@@ -202,6 +202,8 @@ public static TColumnValue toTColumnValue(Type type, Object value) {
     case UNION_TYPE:
     case USER_DEFINED_TYPE:
       return stringValue((String)value);
+    case NULL_TYPE:
+      return stringValue((String)value);
     default:
       return null;
     }