Scala Slick - Identify which DBIO is failing in DBIO.sequence

Question

I'm executing transactionally 3 different operations on DB in the following way

// firstDBIO, secondDBIOA, thirdDBIO: DBIOAction[Unit]

F.delay {
  val unitOfWork = DBIO.sequence(
    List(
      firstDBIO,
      secondDBIO,
      thirdDBIO,
    ),
  )
  db.run(unitOfWork.transactionally)
}.futureLift.void.map(_.asRight[ImportError]).recover {
  case ex: SQLException => Left(ImportError.UnexpectedError)
}

This works correctly but, when the transaction fails, in the recover I can't make logic based on which of the DBIO caused the error (I don't want to rely on the SQLException).

I would like to be able to do something like

.recover {
  case ex: ImportError.CauseFirst => ...
  case ex: ImportError.CauseSecond => ...
  case ex: ImportError.CauseThird => ...
  ...
}

Answer 1

I found that this solution is exactly what I was looking for

dbio.asTry.flatMap {
  case Success(v) => DBIO.successful(v)
  case Failure(e) => DBIO.failed(ImportError.CauseFirst)
}

It preserves the success/failure outcome triggering the abortion of the atomic transaction as requested. In the end, it's just mapping the error contained in the failure, indeed it's quite useful to implement a function to do that

implicit class DBIOOps[A](dbio: DBIO[A]) {
  def mapFailure(f: Throwable => E with Throwable) = dbio.asTry.flatMap {
    case Success(v) => DBIO.successful(v)
    case Failure(e) => DBIO.failed(f(e))
  }
}

F.delay {
  val unitOfWork = DBIO.sequence(
    List(
      firstDBIO.mapFailure(_ => ImportError.CauseFirst),
      secondDBIO.mapFailure(_ => ImportError.CauseSecond),
      thirdDBIO.mapFailure(_ => ImportError.CauseThird),
      ...
    ),
  )
  db.run(unitOfWork.transactionally)
}.futureLift.void.map(_.asRight[ImportError]).recover {
  case ex: ImportError.CauseFirst => ...
  case ex: ImportError.CauseSecond => ...
  case ex: ImportError.CauseThird => ...
  ...
}