Can't do the most basic query in Slick 3

[Josh]

I'm trying to figure out how to run a very basic query in Slick 3.0.0.RC1:

val customers = TableQuery[Customers]
val query = customers.filter(_.customerId == 5)

Now what?

All the tutorials and documentation I've read have said to use query.result (doesn't exist) or query.run (also doesn't exist)

I've been stuck on this for a few hours now and it has given me a headache (literally).

Thanks for any help!

[Josh]

Also, I think it's a separate issue completely but this doesn't compile in my IDE:

class Customers(tag: Tag) extends Table[Customer](tag, "Customers") {
    // columns here
    def projection = LiftedCustomer(customerId.?, customerName)
    override def * = projection
}


object CaseClassMappers {
  implicit object CustomerShape extends CaseClassShape(LiftedCustomer.tupled, Customer.tupled)
}

It says the type of projection, LiftedCustomer, doesn't conform to ProvenShape[Customer] 

I'm using IntelliJ/Scala 2.11.6

I think it might just be the IDE though so maybe not a problem. Has anyone else experienced this?

[sim]

 Here is an example from my prj:

// search  a key in keys table on key_id
  def findCard(cardId: String) = {
    val qa: DBIO[Seq[Key]] = keys.filter(k => k.key_id === cardId).result
    def res = bagira_db.run(qa)
    res
  }

works fine

[Josh]

Ok.. where did you get that triple equals method/operator from? It is not a recognized symbol for me

and filter returns a slick.lifted.Query:

https://github.com/slick/slick/blob/master/slick/src/main/scala/slick/lifted/Query.scala

I can't see 'result' anywhere there

Where is it coming from?

:/

[Pedro Furlanetto]

Josh, you are missing some essential imports. Like "import
scala.slick.driver.H2Driver.simple._", replace H2Driver with the one
you need.

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[Josh]

Hi Pedro,

I am importing the api like this:

import com.typesafe.slick.driver.db2.DB2Driver.api._

It says `simple` has been deprecated so I should import api instead.

[sim]

 From Slick  doc -

--
Note the use of === instead of == for comparing two values for equality. Similarly, the lifted embedding uses =!= instead of != for inequality. (The other comparison operators are the same as in Scala: <, <=, >=, >.)

--
http://slick.typesafe.com/doc/3.0.0-RC1/gettingstarted.html

[Josh]

Ok thanks, I've got it compiling now. I think I was getting confused because Intellij Scala plugin doesn't seem to recognise the result method which is somehow on the Query object, but it is in fact compiling ok :)

I'm having some trouble working with Futures though, e.g. to do an insert which returns the inserted row's autoinc id:

1. def createUser(user: Json.User)(implicit db: Database): Future[Int] = {
2.     val users = TableQuery[Users]
3.     val action = (users returning users.map(_.userId)) += Models.User(None, user.name)
4.     val x = db.run(action)
5.     x
6. }

This compiles fine, but I get a runtime exception when I call this method:

java.lang.ClassCastException: Cannot cast scala.concurrent.impl.Promise$DefaultPromise to java.lang.Integer

I debugged and saw that x.value is Some(Success(3))      (where 3 is the id column being returned)

Do you have any ideas what's wrong here? Sorry if it's a stupid question I'm still getting used to working with Futures

[sim]

another exapmple for insert:

// write a pass to passes table
  def cdr(clId: Long,crdId: String,trmId: String) = {
    val qa: DBIO[Int] = passes.map(p => p.forIns) += (clId,crdId,trmId)

[Josh]

well, my insert is working (as in, it is inserting the row) it's just I can't figure out how to return the Future[Int] that I want to return (representing the id of the row that gets inserted)

It seems the future value ends up being Some(Success(id)) 

I've been trying to figure out how to check the SQL being executed too.. but it just doesn't work like it says in the documentation: http://slick.typesafe.com/doc/3.0.0-RC1/queries.html?highlight=querying

It says to do query_action.statements to retrieve the SQL, but there is no statements method on type DBIO[...]!

Maybe I'll try the previous version of Slick and see if things are easier...

[sim]

You can do something like that:

your Future map(result => result.id match {
     case id: Int => do something
     case _ => do something })

[Viktor Klang]

Is 'x' a Future[Int] or Future [Nothing]?

(It always helps to add explicit types if your types don't add up)

--
Cheers,
√

——————
Viktor Klang
Chief Architect

Typesafe Inc.

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/18d4e86b-c2ba-4150-bc5f-87bedd17538f%40googlegroups.com.

[Josh]

You're right it turns out it wasn't a Future[Int]... it was a Future[Future[Int]] !

I think it's because I'm using akka's ask (? method) which itself returns a Future, then inside my database actor I am also using Slick to return a Future[Int]

So I guess it was just me using akka incorrectly, the solution was to do this:

val response = (databaseActor ? CreateUser(user))
  .mapTo[Future[Int]]
  .flatMap(identity)

Not sure if there's a better way as it doesn't seem very nice to return a Future[Future[Int]] but this seems to work...

Thanks for the advice 

[Viktor Klang]

What does the actor's receive method look like, I think you are missing a pipeTo

--
Cheers,
√

——————
Viktor Klang
Chief Architect

Typesafe Inc.

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/a33d39bf-d2ef-4b7d-9ec3-cc7b90cc7857%40googlegroups.com.

[Josh]

Hmm ok, it looks like this at the moment:

http://pastebin.com/jwW94k5M

Should I be using pipeTo here? I'm not really sure why/when pipeTo should be used instead of tell.

Thanks,

Josh

[Luis Ángel Vicente Sánchez]

If the function returns a future, you should use pipeTo sender.

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/e0b9bdbe-e214-43e0-949d-8c0c95f43761%40googlegroups.com.

[Viktor Klang]

Assuming the UserDAO methods return futures:

def receive = {
    case CreateUser(user) =>
      UserDAO.createUser(user) pipeTo sender()
    case GetUserById(id) =>
      userDAO.getUserById(id) pipeTo sender()
  }

--
Cheers,
√

——————
Viktor Klang
Chief Architect

Typesafe Inc.

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/e0b9bdbe-e214-43e0-949d-8c0c95f43761%40googlegroups.com.

[Josh]

Thanks for the help, this works well :)

[Viktor Klang]

You're most welcome!

--
Cheers,
√

——————
Viktor Klang
Chief Architect

Typesafe Inc.

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/2434d3c2-aa4f-4a89-8742-cd40625570c3%40googlegroups.com.

[Josh]

Does anyone know how to view the SQL statements being executed by Slick?

The documentation here: http://slick.typesafe.com/doc/3.0.0-RC1/queries.html?highlight=statements  says to use query_action.statements

But this doesn't compile for me:

val qa: DBIO[Seq[Models.User]] = query.result
println(qa.statements.head)

because the statements symbol is not found

[Stefan Zeiger]

On 2015-03-10 14:39, Josh wrote:

Does anyone know how to view the SQL statements being executed by Slick?

The documentation here: http://slick.typesafe.com/doc/3.0.0-RC1/queries.html?highlight=statements  says to use query_action.statements

But this doesn't compile for me:

val qa: DBIO[Seq[Models.User]] = query.result
println(qa.statements.head)

Remove the type annotation. Features like this which are not available for all DBIOActions are defined on specific subtypes (in this case, you need at least SqlAction[Seq[Models.User], NoStream, Effect.All]).

--
Stefan Zeiger
Slick Tech Lead
Typesafe - Build Reactive Apps!
Twitter: @StefanZeiger

[Josh]

Thanks! That works

I was using the type annotation because IntelliJ scala plugin doesn't seem to be able to figure out the type of query.result

and without the type annotation it makes it much more difficult to work with the query result in the IDE

[Kabir Idris]

Hi all, how do a retrieve the value from the future returned?

I know I can use the map , flatmap and for-expression  to manipulate the returned value but unfortunately, it will also return a future of either a success or failure
I want the return future to be a string or case class object
e.g I want to do something like this

val m = applicant.filter(_.id === "123").result

val query = db.run(m) // this is a future object

val name = query.map(_.name) //unfortunately val name is also a future and not a string

println(name)   // will return scala.concurrent.impl.Promise$DefaultPromise@69ee8449

[Matthew Ewer]

GOOD GOLLY, FINALLY.  Finally figured out how to do what I (and you) want.  So, I understand that this is apparently bad form, breaks rules, etc.  But if you just want to get your dang data and be done, the key is basically "Await.result()".  For example:

Await.result(db.run(users.map(_.name).result), Duration.Inf)

Assuming all the code's in place to set up the users table and everything, this should give you a Seq[String] of the names of all the users.