Build dynamic UPDATE query in Slick 3 - scala

Question

I am looking for a way to generate an UPDATE query over multiple columns that are only known at runtime.
For instance, given a List[(String, Int)], how would I go about generating a query in the form of UPDATE <table> SET k1=v1, k2=v2, kn=vn for all key/value pairs in the list?
I have found that, given a single key/value pair, a plain SQL query can be built as sqlu"UPDATE <table> SET #$key=$value (where the key is from a trusted source to avoid injection), but I've been unsuccessful in generalizing this to a list of updates without running a query for each.
Is this possible?

Answer 1

This is one way to do it. I create a table definition T here with table and column names (TableDesc) as implicit arguments. I would have thought that it should be possible to set them explicitly, but I couldn't find it. For the example a create to table query instances, aTable and bTable. Then I insert and select some values and in the end I update a value in the bTable.
import slick.driver.H2Driver.api._
import scala.concurrent.Await
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.Duration
import scala.util.{Failure, Success}
val db = Database.forURL("jdbc:h2:mem:test1;DB_CLOSE_DELAY=-1", "sa", "", null, "org.h2.Driver")
case class TableDesc(tableName: String, intColumnName: String, stringColumnName: String)
class T(tag: Tag)(implicit tableDesc: TableDesc) extends Table[(String, Int)](tag, tableDesc.tableName) {
def stringColumn = column[String](tableDesc.intColumnName)
def intColumn = column[Int](tableDesc.stringColumnName)
def * = (stringColumn, intColumn)
}
val aTable = {
implicit val tableDesc = TableDesc("TABLE_A", "sa", "ia")
TableQuery[T]
}
val bTable = {
implicit val tableDesc = TableDesc("TABLE_B", "sb", "ib")
TableQuery[T]
}
val future = for {
_ <- db.run(aTable.schema.create)
_ <- db.run(aTable += ("Hi", 1))
resultA <- db.run(aTable.result)
_ <- db.run(bTable.schema.create)
_ <- db.run(bTable ++= Seq(("Test1", 1), ("Test2", 2)))
_ <- db.run(bTable.filter(_.stringColumn === "Test1").map(_.intColumn).update(3))
resultB <- db.run(bTable.result)
} yield (resultA, resultB)
Await.result(future, Duration.Inf)
future.onComplete {
case Success(a) => println(s"OK $a")
case Failure(f) => println(s"DOH $f")
}
Thread.sleep(500)
I've got the sleep statement in the end to assert that the Future.onComplete gets time to finish before the application ends. Is there any other way?