Slick 3.0 how to update variable column list, which number is know only in Runtime

问题

Is it possible to update variable column list, which number is know only in runtime by slick 3.0?

Below is example what I want to do (won't compile)

var q: Query[UserTable, UserTable#TableElementType, Seq] = userTable
var columns = List[Any]()
var values = List[Any]()

if (updateCommands.name.isDefined) {
  columns = q.name :: columns
  values = updateCommands.name.get :: values
}

if (updateCommands.surname.isDefined) {
  columns = q.surname :: columns
  values = updateCommands.surname.get :: values
}
q = q.filter(_.id === updateCommands.id).map(columns).update(values)

回答1:

Here is what I've done in Slick 3.1. I wasn't sure what worse, editing plain SQL statement or multiple queries. So I decided to go with latter assuming Postgres optimizer would see same WHERE clause in update queries of single transaction. My update method looks like this

def updateUser(user: User, obj: UserUpdate): Future[Unit] = {

  val actions = mutable.ArrayBuffer[DBIOAction[Int, NoStream, Write with Transactional]]()
  val query = users.withFilter(_.id === user.id)

  obj.name.foreach(v => actions += query.map(_.name).update(v))
  obj.email.foreach(v => actions += query.map(_.email).update(Option(v)))
  obj.password.foreach(v => actions += query.map(_.pwdHash).update(Option(encryptPassword(v))))

  slickDb.run(DBIO.seq(actions.map(_.transactionally): _*))
}

回答2:

In Slick 3.0 they adopted slightly different approach, instead of having updateAll methods, as far as I userstand path of combinators was adopted.

So main idea is to define some actions on the data and then combine them ont he database to make a single run. Example:

// let's assume that you have some table classes defined somewhere

// then let's define some actions, they might be really different
val action: SqlAction = YourTable.filter(_id === idToAssert)
val anotherAction = AnotherTable.filter(_.pets === "fun")

// and then we can combine them on a db.run 
val combinedAction =  for {
  someResult <- action
  anotherResult <- anotherAction
} yeild (someResult,anotherResult)

db.run(combinedAction) // that returns actual Future of the result type

In the same way you can deal with lists and sequences, for that please take a look here: http://slick.typesafe.com/doc/3.1.0-M1/dbio.html DBIO has some functions that allows you to combine list of actions to one action.

I hope that idea is clear, if you have questions you are wellcome to the comments.

回答3:

to update a variable number of columns you may use this way as I used for slick 3:

  def update(id: Long, schedule: Schedule, fieldNames: Seq[String]): Future[_] = {
val columns = schedules.baseTableRow.create_*.map(_.name).toSeq.filter(fieldNames.map(_.toUpperCase).contains)
val toBeStored = schedule.withDefaults

val actions = mutable.ArrayBuffer[DBIOAction[Int, NoStream, Write with Transactional]]()
val query = schedules.withFilter(_.id === id)

//this is becasue of limitations in slick, multiple columns are not possible to be updated!

columns.find("NAME".equalsIgnoreCase).foreach(x => actions += query.map(_.name).update(toBeStored.name))
columns.find("NAMESPACE".equalsIgnoreCase).foreach(x => actions += query.map(_.namespace).update(toBeStored.namespace))
columns.find("URL".equalsIgnoreCase).foreach(x => actions += 

db.run(DBIO.seq(actions: _ *).transactionally.withPinnedSession)

}

来源：https://stackoverflow.com/questions/32464435/slick-3-0-how-to-update-variable-column-list-which-number-is-know-only-in-runti

标签

scala

slick-3.0