scala - 从灵活查询中的多个表中删除行

Question

我用谷歌搜索并找到了这个线程 Slick 3.0: Delete rows from multiple tables in a transaction但是解决方案说这不是一个好的解决方案。

我正在使用下面的代码从多个表中删除行

val deleteB = for {
  aId <- TableA.filter(a => a.id === param).map(_.id)
  bId <- TableB.filter(_.aId === aId)
} yield bId

val deleteC = for {
  aId <- TableA.filter(a => a.id === param).map(_.id)
  cId <- TableC.filter(_.aId === aId)
} yield cId

val deleteA = TableA.filter(a.Id === param)

val query = (deleteC.delete andThen deleteB.delete andThen deleteA.delete).transactionally
db.run(query)

但我想知道是否有更好的写法。

上述方法的问题是我想返回从 TableA 中删除的行数，而不是从子表 TableB 和 TableC 中删除的行的总和。

此外，在运行时它会提示在删除查询中有连接。

Answer 1

我想你也可以这样做-

 def buildTransactionQuery = {
    for {
      deleteA <- TableA.filter(a.Id === param)
      deleteB  <- TableB.filter(_.aId === deleteA.map(_.id))
      deleteC  <- TableC.filter(_.aId === deleteA.map(_.id))

      deleteAAction = deleteA.delete
      deleteBAction = deleteB.delete
      deleteCAction = deleteC.delete
      res = (deleteAAction, deleteBAction, deleteCAction)
    } yield res
  }

  def executeTransactionQuery = {
    val transactionQuery = for {
      queries <- buildTransactionQuery
      action = DBIOAction.seq(queries._3, queries._2, queries._1)
    } yield action
    transactionQuery.flatMap(action => db.run(action.transactionally).transform(s => true, t => {
      logger.error(t.getMessage)
      t
    }))
  }