From 51b514316214b2946c72201b4594e6f480665b2b Mon Sep 17 00:00:00 2001
From: praveenbingo <praveen@dremio.com>
Date: Thu, 14 Feb 2019 00:13:18 +0530
Subject: [PATCH] ARROW-4539: [Java] Fix child vector count for lists. (#3625)

* ARROW-4539: [Java] Fix child vector count for lists.

- Child vector count was not set correctly for lists. Fixed to use the right count.

* ARROW-4539: [Java] Add license header.
---
 .../arrow/vector/complex/ListVector.java      |  2 +-
 .../arrow/vector/TestVarCharListVector.java   | 78 +++++++++++++++++++
 2 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 java/vector/src/test/java/org/apache/arrow/vector/TestVarCharListVector.java

diff --git a/java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java b/java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java
index 067060a4f7fa7..7d98f71477d1a 100644
--- a/java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java
+++ b/java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java
@@ -744,7 +744,7 @@ public void setValueCount(int valueCount) {
     }
     /* valueCount for the data vector is the current end offset */
     final int childValueCount = (valueCount == 0) ? 0 :
-            offsetBuffer.getInt(valueCount * OFFSET_WIDTH);
+            offsetBuffer.getInt(lastSet * OFFSET_WIDTH);
     /* set the value count of data vector and this will take care of
      * checking whether data buffer needs to be reallocated.
      */
diff --git a/java/vector/src/test/java/org/apache/arrow/vector/TestVarCharListVector.java b/java/vector/src/test/java/org/apache/arrow/vector/TestVarCharListVector.java
new file mode 100644
index 0000000000000..5dd2a9835e55b
--- /dev/null
+++ b/java/vector/src/test/java/org/apache/arrow/vector/TestVarCharListVector.java
@@ -0,0 +1,78 @@
+/*
+ * 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.arrow.vector;
+
+import org.apache.arrow.memory.BufferAllocator;
+import org.apache.arrow.vector.complex.ListVector;
+import org.apache.arrow.vector.complex.impl.UnionListWriter;
+import org.apache.arrow.vector.types.Types;
+import org.apache.arrow.vector.types.pojo.FieldType;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import io.netty.buffer.ArrowBuf;
+
+public class TestVarCharListVector {
+
+  private BufferAllocator allocator;
+
+  @Before
+  public void init() {
+    allocator = new DirtyRootAllocator(Long.MAX_VALUE, (byte) 100);
+  }
+
+  @After
+  public void terminate() throws Exception {
+    allocator.close();
+  }
+
+  @Test
+  public void testVarCharListWithNulls() {
+    byte[] bytes = "a".getBytes();
+    try (ListVector vector = new ListVector("VarList", allocator, FieldType.nullable(Types
+            .MinorType.VARCHAR.getType()),null);
+         ArrowBuf tempBuf = allocator.buffer(bytes.length)) {
+      UnionListWriter writer = vector.getWriter();
+      writer.allocate();
+
+      // populate input vector with the following records
+      // ["a"]
+      // null
+      // ["b"]
+      writer.setPosition(0); // optional
+      writer.startList();
+      tempBuf.setBytes(0, bytes);
+      writer.writeVarChar(0, bytes.length, tempBuf);
+      writer.endList();
+
+      writer.setPosition(2);
+      writer.startList();
+      bytes = "b".getBytes();
+      tempBuf.setBytes(0, bytes);
+      writer.writeVarChar(0, bytes.length, tempBuf);
+      writer.endList();
+
+      writer.setValueCount(2);
+
+      Assert.assertTrue(vector.getValueCount() == 2);
+      Assert.assertTrue(vector.getDataVector().getValueCount() == 2);
+    }
+  }
+}