Lift a Scala function to a database function for H2, using Code.lift

LiftFunction.scala

package org.scalaquery.demo

import scala.reflect._
import org.scalaquery.ql._
import org.scalaquery.ql.extended.{ExtendedTable => Table}
import org.scalaquery.ql.extended.H2Driver.Implicit._
import org.scalaquery.simple.StaticQuery.updateNA
import org.scalaquery.session.Database
import org.scalaquery.session.Database.threadLocalSession

object LiftFunction extends App {

  // H2 expects user-defined functions as public static methods
  def mixedCase(s: String): String = s grouped 2 map { g =>
    g(0).toUpper + (if(g.length == 1) "" else g(1).toLower.toString)
  } mkString

  // We use an embedded DB, so the function above is automatically on the class-path
  Database.forURL("jdbc:h2:mem:test1", driver = "org.h2.Driver") withSession {

    // Define a table and populate it with some values
    object Users extends Table[String]("USERS") {
      def name = column[String]("NAME")
      def * = name
    }
    Users.ddl.create
    Users.insert("szeiger")
    Users.insert("guest")

    // Lift a public static method to a DB function
    def createAlias[T1, R: TypeMapper](code: Code[T1 => R]) = {
      // Get the FQN of the method from the AST
      val Block(_, Function(_, Apply(Select(_, Method(n, _)), _))) = code.tree
      // Define the function in the DB
      updateNA("create alias if not exists \""+n+"\" for \""+n+"\"").execute
      // Return a ScalaQuery function for it
      SimpleFunction.unary[T1, R]("\""+n+"\"")
    }

    // Lift the mixedCase Scala function to a DB function
    val mixedCaseDB = createAlias(Code.lift(mixedCase _))

    // Use it in a query and print the statement + results
    val q = for {
      u <- Users
    } yield mixedCaseDB(u.name)
    println("q: " + q.selectStatement)
    q.foreach(println)
  }
}

/*

[info] Running org.scalaquery.demo.LiftFunction
q: SELECT "org.scalaquery.demo.LiftFunction.mixedCase"("t1"."NAME") FROM "USERS" "t1"
SzEiGeR
GuEsT

*/