DRILL-2066: Clear target vectors before performing transfer()

exec/java-exec/src/main/codegen/templates/FixedValueVectors.java

@@ -159,6 +159,7 @@ public TransferPair makeTransferPair(ValueVector to) {
   }
 
   public void transferTo(${minor.class}Vector target){
+    target.clear();
     target.data = data;
     target.data.retain();
     target.data.writerIndex(data.writerIndex());

exec/java-exec/src/main/codegen/templates/RepeatedValueVectors.java

@@ -100,6 +100,7 @@ public TransferPair makeTransferPair(ValueVector to) {
   }
 
   public void transferTo(Repeated${minor.class}Vector target){
+    target.clear();
     offsets.transferTo(target.offsets);
     values.transferTo(target.values);
     target.parentValueCount = parentValueCount;

exec/java-exec/src/main/codegen/templates/VariableLengthVectors.java

@@ -161,6 +161,7 @@ public TransferPair makeTransferPair(ValueVector to) {
   }
 
   public void transferTo(${minor.class}Vector target){
+    target.clear();
     this.offsetVector.transferTo(target.offsetVector);
     target.data = data;
     target.data.retain();

exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/sort/TestSort.java

@@ -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.drill.exec.physical.impl.sort;
+
+import org.apache.drill.BaseTestQuery;
+import org.junit.Test;
+
+/**
+ * Placeholder for all sort related test. Can be used as we move
+ * more tests to use the new test framework
+ */
+public class TestSort extends BaseTestQuery {
+
+  @Test
+  public void testSortWithComplexInput() throws Exception {
+    test("select t.a from cp.`jsoninput/repeatedmap_sort_bug.json` t order by t.b");
+  }
+}

exec/java-exec/src/test/resources/jsoninput/repeatedmap_sort_bug.json

@@ -0,0 +1 @@
+{"a" : [ {"c": 1} ], "b" : 2.1}