Scala Slick joinLeft and combined conditions - scala

Question

I want to be able to create a query with Slick that let me filter left joins in a dynamic way
case class Player(
id: Long,
createdAt: DateTime,
lastModificationDate: DateTime,
name: String
)
class PlayerTable(tag: Tag) extends Table[Player](tag, "players") {
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def createdAt = column[DateTime]("createdAt")
def lastModificationDate = column[DateTime]("lastModificationDate")
def name = column[String]("name")
override def * : ProvenShape[Player] = (
id,
createdAt,
lastModificationDate,
updatedAt,
name
) <> (Player.tupled, Player.unapply)
}
case class PlayerGame(
id: Long,
createdAt: DateTime,
lastModificationDate: DateTime,
playerId: Long,
level: Int,
status: String
)
class PlayerGameTable(tag: Tag) extends Table[PlayerGame](tag, "player_games") {
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def createdAt = column[DateTime]("createdAt")
def lastModificationDate = column[DateTime]("lastModificationDate")
def playerId = column[Long]("playerId")
def level = column[Int]("level")
def status = column[String]("status")
override def * : ProvenShape[PlayerGame] = (
id,
createdAt,
lastModificationDate,
playerId,
level,
status
) <> (PlayerGame.tupled, PlayerGame.unapply)
}
I want to write a query like this with Slick, where the WHERE CLAUSE is dynamic. I wrote two examples
SELECT *
FROM players
LEFT JOIN player_games AS playerGamesOne ON players.id = playerGamesOne.playerId AND playerGamesOne.level = 1
LEFT JOIN player_games AS playerGamesTwo ON players.id = playerGamesTwo.playerId AND playerGamesTwo.level = 2
WHERE playerGamesOne.status LIKE 'gameOver'
OR playerGamesTWO.status LIKE 'gameOver'
SELECT *
FROM players
LEFT JOIN player_games AS playerGamesOne ON players.id = playerGamesOne.playerId AND playerGamesOne.level = 1
LEFT JOIN player_games AS playerGamesTwo ON players.id = playerGamesTwo.playerId AND playerGamesTwo.level = 2
WHERE playerGamesOne.status LIKE 'playing'
OR playerGamesTwo.status NOT LIKE 'gameOver'
I was trying something like this, but I get Rep[Option[PlayerGameTable]] as the parameter. Maybe there is a different way of doing something like this
val baseQuery = for {
((p, g1), g2) <- PlayerTable.playerQuery joinLeft
PlayerGameTable.playerGameQuery ON ((x, y) => x.id === y.playerId && y.level === 1) joinLeft
PlayerGameTable.playerGameQuery ON ((x, y) => x._1.id === y.playerId && y.level === 2)
} yield (p, g1, g2)
private def filterPlayerGames(gameStatus: String, playerGamesOneOpt: Option[PlayerGameTable], playerGamesTwoOpt: Option[PlayerGameTable]) = {
(gameStatus, playerGamesOneOpt, playerGamesOneOpt) match {
case (gameStatus: String, Some(playerGamesOne: PlayerGameTable), Some(playerGamesOne: PlayerGameTable)) if gameStatus == "gameOver" => playerGamesOne.status === "gameOver" || playerGamesTwo.status === "gameOver"
}
}
It is a complex question, if soemthing is not clear please let me know and I will try to clarify it

Answer 1

There are a couple of issues:
With multiple conditions, the underscore placeholder used within your ON clause would not work the way intended
_.level = something is an assignment, not a condition
Assuming PlayerTable.playerQuery is TableQuery[PlayerTable] and PlayerGameTable.playerGameQuery is TableQuery[PlayerGameTable], your baseQuery should look like this:
val baseQuery = for {
((p, g1), g2) <- PlayerTable.playerQuery joinLeft
PlayerGameTable.playerGameQuery on ((x, y) => x.id === y.playerId && y.level === 1) joinLeft
PlayerGameTable.playerGameQuery on ((x, y) => x._1.id === y.playerId && y.level === 2)
} yield (p, g1, g2)
It's not entirely clear to me how your filterPlayerGames method is going to handle dynamic conditions. Nor do I think any filtering wrapper method will be flexible enough to cover multiple conditions with arbitrary and/or/negation operators. I would suggest that you use the baseQuery for the necessary joins and build filtering queries on top of it, similar to something like below:
val query1 = baseQuery.filter{ case (_, g1, g2) =>
g1.filter(_.status === "gameOver").isDefined || g2.filter(_.status === "gameOver").isDefined
}
val query2 = baseQuery.filter{ case (_, g1, g2) =>
g1.filter(_.status === "playing").isDefined || g2.filter(_.status =!= "gameOver").isDefined
}
Note that with the left joins, g1 and g2 are of Option type, thus isDefined is applied for the or operation.
On a separate note, given that your filtering conditions are only on PlayerGameTable, it would probably be more efficient to perform filtering before the joins.