Null value comparision in slick - slick

Question

I encounter a problem of nullable column comparison.
If some columns are Option[T], I wonder how slick translate like === operation on these columns to sql.
There are two possibilities: null value( which is None in scala ) and non-null value.
In the case of null value, sql should use is instead of =.
However slick doesn't handle it correctly in the following case.
Here is the code (with H2 database):
object Test1 extends Controller {
case class User(id: Option[Int], first: String, last: String)
class Users(tag: Tag) extends Table[User](tag, "users") {
def id = column[Int]("id",O.Nullable)
def first = column[String]("first")
def last = column[String]("last")
def * = (id.?, first, last) <> (User.tupled, User.unapply)
}
val users = TableQuery[Users]
def find_u(u:User) = DB.db.withSession{ implicit session =>
users.filter( x=> x.id === u.id && x.first === u.first && x.last === u.last ).firstOption
}
def t1 = Action {
DB.db.withSession { implicit session =>
DB.createIfNotExists(users)
val u1 = User(None,"123","abc")
val u2 = User(Some(1232),"123","abc")
users += u1
val r1 = find_u(u1)
println(r1)
val r2 = find_u(u2)
println(r2)
}
Ok("good")
}
}
I print out the sql. It is following result for the first find_u.
[debug] s.s.j.J.statement - Preparing statement: select x2."id", x2."first", x2."last" from "users" x2 where (
(x2."id" = null) and (x2."first" = '123')) and (x2."last" = 'abc')
Notice that (x2."id" = null) is incorrect here. It should be (x2."id" is null).
Update:
Is it possible to only compare non-null fields in an automatic fashion? Ignore those null columns.
E.g. in the case of User(None,"123","abc"), only do where (x2."first" = '123')) and (x2."last" = 'abc')

Answer 1

Slick uses three-valued-logic. This shows when nullable columns are involved. In that regard it does not adhere to Scala semantics, but uses SQL semantics. So (x2."id" = null) is indeed correct under these design decisions. To to a strict NULL check use x.id.isEmpty. For strict comparison do
(if(u.id.isEmpty) x.id.isEmpty else (x.id === u.id))
Update:
To compare only when the user id is non-null use
(u.id.isEmpty || (x.id === u.id)) && ...