Slick codegen & tables with > 22 columns

Question

I\'m new to Slick. I\'m creating a test suite for a Java application with Scala, ScalaTest and Slick. I\'m using slick to prepare data before the test and to do assertions o

Answer 1

There are few options available as you have already found out - nested tuples, conversion from Slick HList to Shapeless HList and then to case classes and so on.

I found all those options too complicated for the task and went with customised Slick Codegen to generate simple wrapper class with accessors.

Have a look at this gist.

class MyCodegenCustomisations(model: Model) extends slick.codegen.SourceCodeGenerator(model){
import ColumnDetection._


override def Table = new Table(_){
    table =>

    val columnIndexByName = columns.map(_.name).zipWithIndex.toMap
    def getColumnIndex(columnName: String): Option[Int] = {
        columnIndexByName.get(columnName)

    }

    private def getWrapperCode: Seq[String] = {
        if (columns.length <= 22) {
            //do not generate wrapper for tables which get case class generated by Slick
            Seq.empty[String]
        } else {
            val lines =
                columns.map{c =>
                    getColumnIndex(c.name) match {
                        case Some(colIndex) =>
                            //lazy val firstname: Option[String] = row.productElement(1).asInstanceOf[Option[String]]
                            val colType = c.exposedType
                            val line = s"lazy val ${c.name}: $colType = values($colIndex).asInstanceOf[$colType]"
                            line
                        case None => ""
                    }
                }
            Seq("",
                "/*",
                "case class Wrapper(private val row: Row) {",
                "// addressing HList by index is very slow, let's convert it to vector",
                "private lazy val values = row.toList.toVector",
                ""

            ) ++ lines ++ Seq("}", "*/", "")

        }
    }


    override def code: Seq[String] = {
        val originalCode = super.code
        originalCode ++ this.getWrapperCode
    }


}

}