Filter by existence of many-to-many association example

[antijedi]

For me the example only worked when i added .project(Arel.star) before .exists, so it would look like this:

scope :with_any_role_ids, lambda{ |role_ids|
  # get a reference to the join table
  role_assignments = RoleAssignment.arel_table
  # get a reference to the filtered table
  students = Student.arel_table
  # let AREL generate a complex SQL query
  where(
    RoleAssignment \
      .where(role_assignments[:student_id].eq(students[:id])) \
      .where(role_assignments[:role_id].in([*role_ids].map(&:to_i))) \
      .project(Arel.star) \
      .exists
  )
}

Not sure if it's only in my usecase, but without it I got sql syntax error.

[jhund]

@antijedi thank you for reporting the issue. What version of Rails/ActiveRecord are you using?