I looked into how this could be done, and we could pass the fields to a constructor of a general `AllFieldsQuery` that could be a member of `AbstractIndexQuery`. But then we would pass the concrete fields to use when creating the queries (in `Index.java`). That would scatter the implementation of this query type across `AbstractIndexQuery`, `Index` and the query classes, plus a special case for `Gnd`. I don't think that's an improvement.