How to express Postgres arrays with Scala Slick

Question

I have a table in Postgres 9.5 with this structure:

my_table (id Integer, images_ranks image_rank[]);

where image_rank is:

Answer 1

What is ImageRank? Write its definition. I presume it's a case class

case class ImageRank(imageUrl: String, thumbnailRank: Int)

I guess that besides slick-pg mapper for specific array

implicit val imageRankListTypeMapper =
  new AdvancedArrayJdbcType[ImageRank]("image_rank",
    str => utils.SimpleArrayUtils.fromString[ImageRank](s => {
      val ImageRankRegex = "ImageRank\\((.*),(\\d+)\\)".r
      s match {
        case ImageRankRegex(imageUrl, thumbnailRank) =>
          ImageRank(imageUrl, thumbnailRank.toInt)
        case _ =>
          println(s"$s is not ImageRank")
          ImageRank("", 0)
      }
    })(str).orNull,
    imageRanks => utils.SimpleArrayUtils.mkString[ImageRank](_.toString)(imageRanks)
  ).to(_.toList)

you should define slick mapper for ImageRank like

case class LiftedImageRank(imageUrl: Rep[String], thumbnailRank: Rep[Int])
implicit object ImageRankShape extends CaseClassShape(LiftedImageRank.tupled, ImageRank.tupled)

Documentation is here.

SimpleArrayJdbcType has String argument meaning SQL base type so I guess "image_rank[]" won't work.

Also SimpleArrayJdbcType works with arrays whose base type T is standard and for which ElemWitness[T] is defined in slick-pg. Since there is no ElemWitness[ImageRank] you should use AdvancedArrayJdbcType.

Answer 2

The best would be for you to use this excellent library: https://github.com/tminglei/slick-pg

If you would rather implement it yourself, have a look at the source code (https://github.com/tminglei/slick-pg/tree/master/core/src/main/scala/com/github/tminglei/slickpg/array) and get what you want from there.