fix list vector

Author: julienledem

java/vector/src/main/java/org/apache/arrow/vector/VectorLoader.java

@@ -29,22 +29,37 @@
 import org.apache.arrow.vector.types.pojo.Field;
 import org.apache.arrow.vector.types.pojo.Schema;
 
+import com.google.common.collect.Iterators;
+
 import io.netty.buffer.ArrowBuf;
 
+/**
+ * Loads buffers into vectors
+ */
 public class VectorLoader {
   private final List<FieldVector> fieldVectors;
   private final List<Field> fields;
 
+  /**
+   * will create children in root based on schema
+   * @param schema the expected schema
+   * @param root the root to add vectors to based on schema
+   */
   public VectorLoader(Schema schema, FieldVector root) {
     super();
     this.fields = schema.getFields();
     root.initializeChildrenFromFields(fields);
     this.fieldVectors = root.getChildrenFromFields();
     if (this.fieldVectors.size() != fields.size()) {
-      throw new IllegalArgumentException(); //TODO
+      throw new IllegalArgumentException("The root vector did not create the right number of children. found " + fieldVectors.size() + " expected " + fields.size());
     }
   }
 
+  /**
+   * Loads the record batch in the vectors
+   * will not close the record batch
+   * @param recordBatch
+   */
   public void load(ArrowRecordBatch recordBatch) {
     Iterator<ArrowBuf> buffers = recordBatch.getBuffers().iterator();
     Iterator<ArrowFieldNode> nodes = recordBatch.getNodes().iterator();
@@ -53,6 +68,9 @@ public void load(ArrowRecordBatch recordBatch) {
       FieldVector fieldVector = fieldVectors.get(i);
       loadBuffers(fieldVector, field, buffers, nodes);
     }
+    if (nodes.hasNext() || buffers.hasNext()) {
+      throw new IllegalArgumentException("not all nodes and buffers where consumed. nodes: " + Iterators.toString(nodes) + " buffers: " + Iterators.toString(buffers));
+    }
   }
 
   private void loadBuffers(FieldVector vector, Field field, Iterator<ArrowBuf> buffers, Iterator<ArrowFieldNode> nodes) {

java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java

@@ -51,7 +51,7 @@
 
 public class ListVector extends BaseRepeatedValueVector implements FieldVector {
 
-  UInt4Vector offsets;// TODO: THis masks the same vector in the parent
+  final UInt4Vector offsets;// TODO: THis masks the same vector in the parent which is assigned to this in the constructor.
   final UInt1Vector bits;
   private Mutator mutator = new Mutator();
   private Accessor accessor = new Accessor();
@@ -62,7 +62,7 @@ public class ListVector extends BaseRepeatedValueVector implements FieldVector {
   public ListVector(String name, BufferAllocator allocator, CallBack callBack) {
     super(name, allocator);
     this.bits = new UInt1Vector("$bits$", allocator);
-    offsets = getOffsetVector();
+    this.offsets = getOffsetVector();
     this.writer = new UnionListWriter(this);
     this.reader = new UnionListReader(this);
     this.callBack = callBack;
@@ -92,7 +92,7 @@ public void loadFieldBuffers(ArrowFieldNode fieldNode, List<ArrowBuf> ownBuffers
       throw new IllegalArgumentException("Lists have a validity and offset vector. Found: " + ownBuffers);
     }
     this.bits.load(ownBuffers.get(0));
-    this.offsets.load(ownBuffers.get(0));
+    this.offsets.load(ownBuffers.get(1));
   }
 
   @Override