ActiveRecord find ordering

ActiveRecord find can return multiple records. Unfortunately, database defaults conspire to potentially surprise us later.

user_ids = [123, 37, 42]

# works!
users = User.find(user_ids)
users = company.users.find(user_ids)

# not guaranteed to work
users = company.users.where(id: user_ids)

The thing to be careful for here is some ways that aren’t guaranteed to work may appear to work due to natural ordering in the database. That is, due to index layout or other hijinks you have no control over as a Rails developer, you could pass IDs out of order, like user_ids above, and they’d come back in the right order by happenstance but not for every single case. AR find with an array of IDs is defined in the API docs to preserve order. So if it doesn’t, it’s a bug in AR and not your code.