Loading unrelated entities in one call

I'm working on an Azure based system where database calls are potentially very slow and expensive, so getting as much data back in the one query is important. I can see how to use aggregates to load related data, but how do I load unrelated data?

The example is that I want to insert a row in a table that has foreign keys to 3 other tables. I need to validate the existence of the three foreign key rows and also find out if I already have an entry in the main table based on these 3 foreign key values. If not, I will add the row.

I can't see a way of doing this currently, but something that could preload the cache in a batch mode would be good. By way of example:

    // WARNING: Not real code!!
   using (var uow = GetContext().CreateUnitOfWork()) {
       uow.BeginBatchLoad();
       uow.ForeignOnes.Preload(row => row.Id == fk1);
       uow.ForeignTwos.Preload(row => row.Id == fk2);
       uow.ForeignThrees.Preload(row => row.Id == fk3);
       uow.Details.Preload(row => row.Fk1 == fk1 && row.Fk2 == fk2 && row.Fk3 == fk3);
       uow.DoBatchLoad();

       if (!uow.OfType<Detail>().Any(row => row.Fk1 == fk1 && row.Fk2 == fk2 && row.Fk3 == fk3)) {
          new MainTable {
             Fk1 = fk1,
             Fk2 = fk2,
             Fk3 = fk3
          };
       }
    }

This might also solve the problem of LS developers wishing to hand craft the sql for various entities, but still allow loading the data for multiple entities in the one database call. Also, I could see it being useful for loading master table data for multiple tables prior to sending it down to the client.

Sorry only the entity and any eager loaded child collections are handled in a single call. We dont have an option for loading multiple entity sets of unrelated data in the same way.

Jeremy