Slick left outer join fetching whole joined row as option
left-join, scala, scala-option, slick
Solution
With the code below you can put it like: yield (user, image.maybe)
case class RemoteImage(id: Long, url: URL)
class RemoteImages extends Table[RemoteImage]("RemoteImage") {
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def url = column[URL]("url", O.NotNull)
def * = id.? ~ url <> (RemoteImage.apply _, RemoteImage.unapply _)
def maybe = id.? ~ url.? <> (applyMaybe,unapplyBlank)
val unapplyBlank = (c:Option[RemoteImage])=>None
val applyMaybe = (t: (Option[Long],Option[URL])) => t match {
case (Some(id),Some(url)) => Some(RemoteImage(Some(id),url))
case _ => None
}
}
Problem
My join looks like this: ``` def byIdWithImage = for { userId <- Parameters[Long] (user, image) <- Users leftJoin RemoteImages on (_.imageId === _.id) if user.id === userId } yield (user, image) ``` but slick fails at runtime when user.imageId is null [SlickException: Read NULL value for column RemoteImage.url] Changing the yield to ``` } yield (user, image.?) ``` gives me a compile time exception, it only works on individual columns could not find implicit value for evidence parameter of type scala.slick.lifted.TypeMapper[image.type] Would there be a different way to accomplish what I'm trying to do here? (in a single query)