Slick 3.0.0 - how to query when an optional field is involved

[Leandro Komosinski]

  Hi,

   Please, consider code below.

case class Seat(id: Int, code: String, observation: Option[String])

class Seats(tag: Tag)  extends Table[Seat](tag, "seats") {
  def id = column[Int]("id", O.PrimaryKey)
  def code = column[String]("code")
  def observation = column[Option[String]]("observation")
  def * = (id, code, observation) <> (Seat.tupled, Seat.unapply)
}

val seats = TableQuery[Seats]

How must I code the query "find all seats with no observation"? Compiler doesn't accept this

seats.filter(_.observation === None)

I wish create a method like this

def findAllSeatsWithoutObservation = {
  db.run(seats.filter(_.observation === None).result)
}

 Thanks,

Leandro

[Naftoli Gugenheim]

On Wed, May 27, 2015 at 2:27 PM Leandro Komosinski <leandro.k...@gmail.com> wrote:

  Hi,

   Please, consider code below.

case class Seat(id: Int, code: String, observation: Option[String])

class Seats(tag: Tag)  extends Table[Seat](tag, "seats") {
  def id = column[Int]("id", O.PrimaryKey)
  def code = column[String]("code")
  def observation = column[Option[String]]("observation")
  def * = (id, code, observation) <> (Seat.tupled, Seat.unapply)
}

val seats = TableQuery[Seats]

How must I code the query "find all seats with no observation"? Compiler doesn't accept this

seats.filter(_.observation === None)

Does it give you any information about why it doesn't accept it? Because if it does it might be helpful to share it. :)

 

I wish create a method like this

def findAllSeatsWithoutObservation = {
  db.run(seats.filter(_.observation === None).result)
}

Does _.observation.isEmpty work?

 

 Thanks,

Leandro

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[Leandro Komosinski]

 No, because _.observation type is Rep[Option[String]] and not Option[String].

And that is precisely the point: why there is no implicit conversion from Option[String] to Rep[Option[String]] as is the case in any other types.

[Naftoli Gugenheim]

On Wed, May 27, 2015, 3:06 PM Leandro Komosinski <leandro.k...@gmail.com> wrote:

 No, because _.observation type is Rep[Option[String]] and not Option[String].

I know that. There are extension methods though.
Are you importing driver.simple._ or driver.api._ ?

And that is precisely the point: why there is no implicit conversion from Option[String] to Rep[Option[String]] as is the case in any other types.

You mean the reverse?

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[Leandro Komosinski]

This is my import

import slick.driver.H2Driver.api._

The same error happens with code below:

class X(tag: Tag) extends Table[(Int, Option[String])](tag, "X") {

    def id = column[Int]("id", O.PrimaryKey)

    def name = column[Option[String]]("name")
    def * = (id, name)
  }

 

val x = TableQuery[X]

def getAllXWithNameNone = {
    db.run(x.filter(_.name === None).result)
  }

Compiler error message is:


ambiguous implicit values:  both value BooleanColumnCanBeQueryCondition in object CanBeQueryCondition of type => slick.lifted.CanBeQueryCondition[slick.lifted.Rep[Boolean]]  and value BooleanOptionColumnCanBeQueryCondition in object CanBeQueryCondition of type => slick.lifted.CanBeQueryCondition[slick.lifted.Rep[Option[Boolean]]]  match expected type slick.lifted.CanBeQueryCondition[Nothing]  

[Leandro Komosinski]

Solved! (but I'm not sure it's the recommended way)

def getAllXWithNameNone = {
  db.run(x.filter( _.name.column.isEmpty).result)
}

Slick's docs (http://slick.typesafe.com/doc/3.0.0/queries.html) could show an example about this case.

[Naftoli Gugenheim]

On Fri, May 29, 2015 at 2:55 AM Leandro Komosinski <leandro.k...@gmail.com> wrote:

This is my import

import slick.driver.H2Driver.api._

You should get access to all these extension methods: https://github.com/slick/slick/blob/883435050da236e2c3229ee11489dd0e28911d3b/slick/src/main/scala/slick/lifted/ExtensionMethods.scala#L174-L224 via https://github.com/slick/slick/blob/883435050da236e2c3229ee11489dd0e28911d3b/slick/src/main/scala/slick/lifted/ExtensionMethods.scala#L237

And I think api should extend ExtensionMethodConversions. Out of curiosity what happens if you write t => anyOptionColumnExtensionMethods(t.column).isEmpty? Does it not find the definition of anyOptionColumnExtensionMethods, or is there some type error somehow?

General rule: if you want to know why an implicit is not being inserted, try it explicitly and see what error you get.

 

The same error happens with code below:

class X(tag: Tag) extends Table[(Int, Option[String])](tag, "X") {

    def id = column[Int]("id", O.PrimaryKey)

    def name = column[Option[String]]("name")
    def * = (id, name)
  }

 

val x = TableQuery[X]

def getAllXWithNameNone = {
    db.run(x.filter(_.name === None).result)
  }

Compiler error message is:


ambiguous implicit values:  both value BooleanColumnCanBeQueryCondition in object CanBeQueryCondition of type => slick.lifted.CanBeQueryCondition[slick.lifted.Rep[Boolean]]  and value BooleanOptionColumnCanBeQueryCondition in object CanBeQueryCondition of type => slick.lifted.CanBeQueryCondition[slick.lifted.Rep[Option[Boolean]]]  match expected type slick.lifted.CanBeQueryCondition[Nothing]  

I think that usually means there's another error message and this one is just a domino effect. Where else is it getting the Nothing from?

 

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[Naftoli Gugenheim]

On Fri, May 29, 2015 at 4:34 AM Leandro Komosinski <leandro.k...@gmail.com> wrote:

Solved! (but I'm not sure it's the recommended way)

def getAllXWithNameNone = {
  db.run(x.filter( _.name.column.isEmpty).result)
}

Strange. Can your IDE tell us where the `column` method is coming from?

 

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[Leandro Komosinski]

I'm using Eclipse. It shows column as a field of slick.lifted.ColumnOrdered

[Leandro Komosinski]

Em sexta-feira, 29 de maio de 2015 06:01:12 UTC-3, nafg escreveu:

On Fri, May 29, 2015 at 2:55 AM Leandro Komosinski <leandro.k...@gmail.com> wrote:

This is my import

import slick.driver.H2Driver.api._

You should get access to all these extension methods: https://github.com/slick/slick/blob/883435050da236e2c3229ee11489dd0e28911d3b/slick/src/main/scala/slick/lifted/ExtensionMethods.scala#L174-L224 via https://github.com/slick/slick/blob/883435050da236e2c3229ee11489dd0e28911d3b/slick/src/main/scala/slick/lifted/ExtensionMethods.scala#L237

And I think api should extend ExtensionMethodConversions. Out of curiosity what happens if you write t => anyOptionColumnExtensionMethods(t.column).isEmpty? Does it not find the definition of anyOptionColumnExtensionMethods, or is there some type error somehow?

  Same error:

ambiguous implicit values:  both value BooleanOptionColumnCanBeQueryCondition in object CanBeQueryCondition of type => slick.lifted.CanBeQueryCondition[slick.lifted.Rep[Option[Boolean]]]  and value BooleanCanBeQueryCondition in object CanBeQueryCondition of type => slick.lifted.CanBeQueryCondition[Boolean]  match expected type slick.lifted.CanBeQueryCondition[Nothing]