mysql - Slick 3.0 (scala) 查询在运行多次之前不会返回数据(我认为)

Question

所以我对数据库、slick 和 scala 非常(非常)陌生，所以我使用了他们在 http://slick.typesafe.com/doc/3.0.0/gettingstarted.html 上的文档中的示例代码

我的问题是，出于某种原因，我必须多次运行查询才能返回数据。在返回结果之前，我必须至少重新运行它 3-4 次。我使用 for 循环重新运行查询，它们也不一定每次都给我完全相同的结果。

创建两个表如下:

  class Patients(tag: Tag) extends Table[(String, String, Int, String)](tag, "Patientss") {
    def PID = column[String]("Patient Id", O.PrimaryKey)

    def Gender = column[String]("Gender")

    def Age = column[Int]("Age")

    def Ethnicity = column[String]("Ethnicity")

    def * = (PID, Gender, Age, Ethnicity)
  }

  val patientsss = TableQuery[Patients]

  class DrugEffect(tag: Tag) extends Table[(String, String, Double)](tag, "DrugEffectss") {

    def DrugID = column[String]("Drug ID", O.PrimaryKey)

    def PatientID = column[String]("Patient_ID")

    def DrugEffectssss = column[Double]("Drug Effect")

    def * = (DrugID, PatientID, DrugEffectssss)

    def Patient = foreignKey("Patient_FK", PatientID, patientsss)(_.PID)}

 val d_effects = TableQuery[DrugEffect]

然后我使用

创建这些表

  val create_empty = DBIO.seq((patientsss.schema ++ d_effects.schema).create)
  val setup_1 = db.run(create_empty)

我在两个文本文件中有实际数据，我使用缓冲阅读器解析它们。我将所有药物 ID 存储在一个创造性地命名为 DrugIds

的列表中

然后，我开始按照以下方式填写表格

我首先填写 Patients 表:

   while (switch != 1) {

    val Patient = CurPatient.split("\\s+")

    if (Patient(2).toUpperCase() == "NA" || (Patient(2).toFloat % 1 != 0))
      age = -1
    else age = Patient(2).toInt

    val insertPatient: DBIO[Option[Int]] = patientsss ++= Seq(
      (Patient(0), Patient(1), age, Patient(3))
    )       

    var future = db.run(insertPatient)



    CurPatient = PatientReader.readLine()

    if (CurPatient == null)
      switch = 1 //switch to 1

  }

对于 DrugEffects 表，我执行以下操作:

 while (switch != 1) {

    val Effect = CurEffect.split("\\s+")

    for (i <- 1 until DrugIds.size - 1) {
      if (Effect(i).toUpperCase() == "NA")
        d_ef = -1.00

      else d_ef = (Effect(i).toFloat).asInstanceOf[Double]


      val insertEffect: DBIO[Option[Int]] = d_effects ++= Seq(
        (DrugIds(i), Effect(0), d_ef)
      )
      var future2 = db.run(insertEffect)
    }


    CurEffect = EffectReader.readLine()

    if (CurEffect == null)
      switch = 1
  }

然后我使用以下代码运行查询

val q1 = for {
    c <- patientsss
  } yield (c.PID, c.Gender, c.Age, c.Ethnicity)

  db.stream(q1.result).foreach(println)

这应该只是给我 Patient 表中的所有数据，但它不一定会这样做。

有时，我会收到以下错误(但并非总是如此):

java.util.concurrent.RejectedExecutionException: Task slick.backend.DatabaseComponent$DatabaseDef$$anon$3@47089c2c rejected from java.util.concurrent.ThreadPoolExecutor@6453123[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 215]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372)
at scala.concurrent.impl.ExecutionContextImpl$$anon$1.execute(ExecutionContextImpl.scala:136)
at slick.backend.DatabaseComponent$DatabaseDef$class.scheduleSynchronousStreaming(DatabaseComponent.scala:253)
at slick.jdbc.JdbcBackend$DatabaseDef.scheduleSynchronousStreaming(JdbcBackend.scala:38)
at slick.backend.DatabaseComponent$BasicStreamingActionContext.restartStreaming(DatabaseComponent.scala:516)
at slick.backend.DatabaseComponent$BasicStreamingActionContext.request(DatabaseComponent.scala:531)
at slick.backend.DatabasePublisher$$anon$3$$anonfun$onNext$2.apply(DatabasePublisher.scala:50)
at slick.backend.DatabasePublisher$$anon$3$$anonfun$onNext$2.apply(DatabasePublisher.scala:49)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at scala.concurrent.impl.ExecutionContextImpl$AdaptedForkJoinTask.exec(ExecutionContextImpl.scala:121)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.pollAndExecAll(ForkJoinPool.java:1253)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1346)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

如果我运行一个更复杂的查询，我得到的数据与查询的参数是准确的，但同样的问题会出现，即结果要么重复，要么不存在，要么不完整(当我重新运行时查询多次)。

如果可以的话，请像我 5 岁一样解释，或者给我指出可以帮助我解决这些问题的资源

编辑:

bjfletcher 的回答有效(谢谢!)，但现在我有另一个问题:

时不时地，代码会因错误而失败:

    Exception in thread "main" org.h2.jdbc.JdbcSQLException: Table "Patientss" not found; SQL statement:
insert into "Patientss" ("Patient Id","Gender","Age","Ethnicity")  values (?,?,?,?) [42102-162]
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:329)
    at org.h2.message.DbException.get(DbException.java:169)
    at org.h2.message.DbException.get(DbException.java:146)
    at org.h2.command.Parser.readTableOrView(Parser.java:4758)
    at org.h2.command.Parser.readTableOrView(Parser.java:4736)
    at org.h2.command.Parser.parseInsert(Parser.java:954)
    at org.h2.command.Parser.parsePrepared(Parser.java:375)
    at org.h2.command.Parser.parse(Parser.java:279)
    at org.h2.command.Parser.parse(Parser.java:251)
    at org.h2.command.Parser.prepareCommand(Parser.java:217)
    at org.h2.engine.Session.prepareLocal(Session.java:415)
    at org.h2.engine.Session.prepareCommand(Session.java:364)
    at org.h2.jdbc.JdbcConnection.prepareCommand(JdbcConnection.java:1121)
    at org.h2.jdbc.JdbcPreparedStatement.<init>(JdbcPreparedStatement.java:71)
    at org.h2.jdbc.JdbcConnection.prepareStatement(JdbcConnection.java:267)
    at slick.jdbc.JdbcBackend$SessionDef$class.prepareStatement(JdbcBackend.scala:252)
    at slick.jdbc.JdbcBackend$BaseSession.prepareStatement(JdbcBackend.scala:386)
    at slick.jdbc.JdbcBackend$SessionDef$class.withPreparedStatement(JdbcBackend.scala:301)
    at slick.jdbc.JdbcBackend$BaseSession.withPreparedStatement(JdbcBackend.scala:386)
    at slick.driver.JdbcInsertInvokerComponent$BaseInsertInvoker.preparedInsert(JdbcInsertInvokerComponent.scala:177)
    at slick.driver.JdbcInsertInvokerComponent$BaseInsertInvoker$$anonfun$internalInsertAll$1.apply(JdbcInsertInvokerComponent.scala:201)
    at slick.jdbc.JdbcBackend$BaseSession.withTransaction(JdbcBackend.scala:422)
    at slick.driver.JdbcInsertInvokerComponent$BaseInsertInvoker.internalInsertAll(JdbcInsertInvokerComponent.scala:198)
    at slick.driver.JdbcInsertInvokerComponent$BaseInsertInvoker.insertAll(JdbcInsertInvokerComponent.scala:194)
    at slick.driver.JdbcInsertInvokerComponent$InsertInvokerDef$class.$plus$plus$eq(JdbcInsertInvokerComponent.scala:73)
    at slick.driver.JdbcInsertInvokerComponent$BaseInsertInvoker.$plus$plus$eq(JdbcInsertInvokerComponent.scala:152)
    at slick.driver.JdbcActionComponent$InsertActionComposerImpl$$anonfun$$plus$plus$eq$1.apply(JdbcActionComponent.scala:459)
    at slick.driver.JdbcActionComponent$InsertActionComposerImpl$$anonfun$$plus$plus$eq$1.apply(JdbcActionComponent.scala:459)
    at slick.driver.JdbcActionComponent$InsertActionComposerImpl$$anon$8.run(JdbcActionComponent.scala:449)
    at slick.driver.JdbcActionComponent$InsertActionComposerImpl$$anon$8.run(JdbcActionComponent.scala:447)
    at slick.backend.DatabaseComponent$DatabaseDef$$anon$2.liftedTree1$1(DatabaseComponent.scala:231)
    at slick.backend.DatabaseComponent$DatabaseDef$$anon$2.run(DatabaseComponent.scala:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

不会一直发生，但经常发生，我不知道这是什么意思

Answer 1

所有的数据库调用都会立即通过Futures返回给您，即使它们还没有完成操作。这是异步的，不是同步的。

您可以通过以下两种方式之一更改您的代码以适应Futures:

1. 您可以对所有数据库调用使用 Await.result，等待它们完成，例如:Await.result(db.run(insertEffect),持续时间.Inf)

2. 您可以使用 .map(或 .flatMap，如果您从内部使用另一个 Future)，代码你想在数据库操作完成时运行。例如:db.run(insertEffect).map(_ => ... do stuff... )

看看另一个 Stack Overflow thread关于异常的一些想法。