SLICK:如何在另一个查询中使用查询结果

Question

我想执行以下操作：

我想返回一个用户列表，首先按用户"关注"的人排序，其次按一些额外的分数排序。然而，我在下面写的以下代码不起作用，因为资助者是提升的Slick类型，因此从未在列表中找到。

        //The following represents the query for only funders who we are following
        val following_funders:  List[User]  = (
            for {
          funder <- all_funders
          f <- follows if f.followerId === id //get all the current users follower objects
          if f.followeeId === funder.id
        } yield funder
        ).list
      val all_funders_sorted = for {
        funder <- all_funders
        following_funder =  following_funders contains funder
      } yield (funder, following_funder)
      //sort the funders by whether or not they are following the funder and then map it to only the funders (i.e. remove the boolean)
      all_funders_sorted.sortBy(_._2.desc).sortBy(_._1.score.desc).map( x => x._1 )  

感谢所有的帮助！

Answer 1

您需要在Slick中使用id（即主键）。这就是对象在数据库端唯一标识的方式。您不需要执行第一个查询。您可以将其用作第二个组件，而无需首先使用in运算符执行：

    //The following represents the query for only funders who we are following
    val following_funders_ids = (
        for {
      funder <- all_funders
      f <- follows if f.followerId === id //get all the current users follower objects
      if f.followeeId === funder.id
    } yield funder.id
  val all_funders_sorted = for {
    funder <- all_funders
    following_funder = funder.id in following_funders_ids
  } yield (funder, following_funder)
  //sort the funders by whether or not they are following the funder and then map it to only the funders (i.e. remove the boolean)
  all_funders_sorted.sortBy(_._1.impactPoints.desc).sortBy(_._2.desc).map( x => x._1 )   

如果你第一次想按以下方式排序，请注意你的排序顺序是错误的。Slick将.sortBy(_.a).sortBy(_.b)转换为ORDER BY B,A，因为Scala集合就是这样工作的：

scala> List( (1,"b"), (2,"a") ).sortBy(_._1).sortBy(_._2)
res0: List[(Int, String)] = List((2,a), (1,b))

Answer 2

最终通过使用"inSet"以以下方式解决了问题

        //The following represents the query for only funders who we are following
        val following_funders_ids:  List[Long]  = (
            for {
          funder <- all_funders
          f <- follows if f.followerId === id //get all the current users follower objects
          if f.followeeId === funder.id
        } yield funder.id
        ).list
      val all_funders_sorted = for {
        funder <- all_funders
        following_funder = funder.id inSet following_funders_ids
      } yield (funder, following_funder)
      //sort the funders by whether or not they are following the funder and then map it to only the funders (i.e. remove the boolean)
      all_funders_sorted.sortBy(_._2.desc).sortBy(_._1.impactPoints.desc).map( x => x._1 )