@Override
public Object getStructFieldData(Object data, StructField fieldRef) {
if (data == null) {
return null;
}
ColumnarStructBase struct = (ColumnarStructBase) data;
MyField f = (MyField) fieldRef;
int fieldID = f.getFieldID();
assert (fieldID >= 0 && fieldID < fields.size());
return struct.getField(fieldID);
}