Hack to support an atomic filter and update with RethinkDB. This is useful for supporting something like a locking message queue. The problem here is that return_vals only works for single-row modifications, and filter() and limit() always returns multiple rows. At least, this was the simplest solution I could come up with.

rethinkdb_atomic_filter_and_update.js

r.db("test").table("queue").filter({"available": true}).limit(1).forEach(function (row) {
  return r.db("test").table("queue").get(row("id")).update({"available": false}, {return_vals: true})
})

Could you write an example query that you'd want to run but currently can't? We'll see if we can make it happen :)

@coffeemug: rethinkdb/rethinkdb#348