It can not add join expressions or preload data for you. Flop does not try to be an alternate query DSL - it just adds WHERE, ORDER BY and LIMIT clauses derived from user-generated parameters to existing Ecto queries.
However, you can define join fields, which are basically a mapping from a field alias to a field name on a named binding (see join fields). You will have to ensure that the necessary named bindings are added to the Ecto query you pass to the Flop functions. This approach means that you can filter and sort by anything that Ecto allows to join on: not only associations, but also the results of subqueries. To avoid unnecessary joins, you can retrieve a list of necessary bindings for a given parameter map before building the query (see Flop.bindings/3).
