||BytesRefArrayWritable holds an array reference to BytesRefWritable,
and is able to resize without recreating new array if not necessary.
||BytesRefWritable referenced a section of byte array.
||ColumnarSerDe is used for columnar based storage supported by RCFile.
||ColumnarStruct is different from LazyStruct in that ColumnarStruct's field
Object get parsed at its initialize time when call
ColumnarStruct.init(BytesRefArrayWritable cols), while LazyStruct parse fields in a