Slick - create columns NOT present in the projection

Question

When using tableQuery.ddl.create, it creates only the columns in the projection. However in our use case there are columns which are used ONLY for filtering and/or ordering, so they are not part of the projection, but they need to be created:

case class CacheEntry(source: String, destination: String, hops: Int)

class CacheTable(tag: Tag) extends Table[CacheEntry](tag, "cache") {

  def source        = column[String]("source")
  def destination   = column[String]("dest")
  def hops          = column[Int]("hops")
  def timestamp     = column[LocalDateTime]("ts", O.DBType("timestamp default now"))

  def * = (source, destination, hops) <> ((CacheEntry.apply _).tupled, CacheEntry.unapply)
}

How can we convince Slick to create the timstamp column with TableQuery[CacheTable].ddl.create?

Are we approaching this in the wrong way? We definately do NOT want the ts to show up in the CacheEntry (we could live with it in this case, but we have more complicated cases where this is not desirable)

OlivierBlanvillain OlivierBlanvillain · Accepted Answer · 2015-10-16T12:47:50

You could define something like a case class TimestampedEE](entry: E, timestamp: LocalDateTime), and change your CacheTable to a Table[Timestamped[CacheEntry]]. The def * projection is probably going to look ugly (if don't rely on some shapeless magic), but that's one way to do it.

Slick - create columns NOT present in the projection

1 Answers