I am using select merge to build the query dynamically. But i can’t understand why ecto give me these errors.
this is the query

                            Ecto.Query<from r0 in Room,
                            select: merge(f0, %{"$aggregate": %{"$count": %{^"floor" => count(f0.floor)}}})>

this is the code:

                  from(
                  r in rooms,
                 select_merge: %{"$aggregate": %{"$count": %{^field => count(field(r, ^atom_field))}}}
                 )

and I got this error:

                        struct Room `does not have the key :"$aggregate".

And if i use it in joins:

this is the query:

  from(
    h in Hospital,
    right_join: r in "rooms",
    on: h.id == r.hospital_id,
    where: r.name == ^"room 1" and ^true,
    select: merge(h, %{^:rooms => map(r, [:name, :purpose, :description])})
  )

this is the code:

       from(
      [h, ..., r] in hospital,
      select_merge: %{
        ^String_to_atom(rooms) => map(r, [:fields])
      }
    )

the error is:

     Postgrex expected a binary, got :rooms. Please make sure the value you are passing matches the 
     definition in your table or in your query or convert the value accordingly.

If i change the rooms to string it will throw the same error i am getting in the count query.

May be I am missing something very obvious here.

Any help will be much appreciated

Thanks