No implicit Ordering defined for scala.slick.lifted.ColumnOrdered[Long]

Question

I'm using slick 2.0 via play plugin and the following is my table mapping

class Tasks(tag: Tag) extends Table[Task](tag, "Tasks"){
    def id   = column[Option[Long]]("id", O.PrimaryKey, O.AutoInc)
    def txt  = column[String]("txt")
    def done = column[Boolean]("done")
    def * = (id, txt, done) <> (Task.tupled, Task.unapply)
}

Then, I created TableQuery object like this

val tasks = TableQuery[Tasks]

I used tasks.list to get List[Task] which returns correctly but when I want to sort the result by using tasks.list.sortBy(_.id.get.desc) I got this error instead

No implicit Ordering defined for scala.slick.lifted.ColumnOrdered[Long].

Any idea?

Answer 1

you have to sort first and then call .list():

tasks.sortBy(_.id.desc).list()

When calling list() you are executing the invoker and that's too late to add the sorting on the sql level, of course you can always sort the collection you get back using the list sortBy method.