Left join query with rethinkDB

I have two tables, users and authors. A user can be an author and if so, in the author document there is the id of the user.

What I want to query are all the users that are NOT authors. The equivalent mySQL query would be something like

select * from users left join authors on users.id=authors.userId
where authors.userId is null

What I tried is

r.db('journa').table('authors').outerJoin(
  r.db('journa').table('users'),
  (author, user) => {
    return author.hasFields({'left': 'claimedByUserId'}).not()
  }
)

But it's not working. Any idea on how to achieve it?

You were almost on the right way. You should not invert in the join expression, because it will return a set of all non-matching permutations and you won't be able to detect a required match. The following query seems to accomplish what you need:

r.db('journa')
    .table('users')
    .outerJoin(
        r.db('journa').table('authors'),
        // This is what two sequences are joined upon
        (user, author) => user('id').eq(author('userId'))
    )
    // Joins return `left` and `right`.
    // If there's nothing at the right side, we assume there was no match
    .filter((lr) => lr.hasFields('right').not())
    // Extracting the left table record only
    .map((lr) => lr('left'))