class ContactsDao {
    public List<Contact> getAll() {
        String sql = "select * from contacts as t left join contact_groups as r1 on (t._id = r1.contact_id) left join  ontact_phone_numbers as r2 on (t._id = r2.contact_id)";

        Cursor result = // asking android for cursor.

        while (result.moveToNext()) {
            // Here inefficiency starts:
                // 1. get contact id
                // 2. check if entity for that id is already created:
                    // 2.no: 1. create entity (new Contact()) and add to list
                         2. add contact related data (display name, etc) to entity from cursor
                    // 2.yes: retrieve created entity from memory.
                // 3. get group id
                // 4. Check if entity for that group id is already created:
                    // 4.no: create entity (ask groups dao, probably) and add it to contact's groups list
                    // 4.yes: do nothing group already added.
                // 5. Do step 4 for phone numbers
        }
    }
}