postgresql - 批量插入时 Slick 3.0 中的数据库异常

Question

虽然在 slick 3 中通过批量插入每五秒插入数千条记录，但我得到了

org.postgresql.util.PSQLException: FATAL: sorry, too many clients already

我的数据访问层是这样的:

val db: CustomPostgresDriver.backend.DatabaseDef = Database.forURL(url, user=user, password=password, driver= jdbcDriver)



 override def insertBatch(rowList: List[T#TableElementType]): Future[Long] = {
    val res = db.run(insertBatchQuery(rowList)).map(_.head.toLong).recover{ case ex:Throwable=> RelationalRepositoryUtility.handleBatchOperationErrors(ex)}
//db.close()
        res
      }

  override def insertBatchQuery(rowList: List[T#TableElementType]): FixedSqlAction[Option[Int], NoStream, Write] = {
    query ++= (rowList)
  }

在插入批处理中关闭连接没有效果...它仍然给出相同的错误。

我像这样从我的代码中调用插入批处理:

val temp1 = list1.flatMap { li =>
        Future.sequence(li.map { trip =>
            val data = for {
              tripData <- TripDataRepository.insertQuery( trip.tripData)
              subTripData <- SubTripDataRepository.insertBatchQuery(getUpdatedSubTripDataList(trip.subTripData, tripData.id))
            } yield ((tripData, subTripData))
            val res=db.run(data.transactionally)
          res
//db.close()
        })
      }

如果我在这里工作后关闭连接，如您在注释代码中看到的那样，我会收到错误消息:

java.util.concurrent.RejectedExecutionException: Task slick.backend.DatabaseComponent$DatabaseDef$$anon$2@6c3ae2b6 rejected from java.util.concurrent.ThreadPoolExecutor@79d2d4eb[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 1]

像这样调用没有 Future.sequence 的方法后:

 val temp1 =list.map { trip =>
          val data = for {
            tripData <- TripDataRepository.insertQuery( trip.tripData)
            subTripData <- SubTripDataRepository.insertBatchQuery(getUpdatedSubTripDataList(trip.subTripData, tripData.id))
          } yield ((tripData, subTripData))
          val res=db.run(data.transactionally)
          res
      }

我仍然有太多客户端错误...

Answer 1

这个问题的根源在于您同时启动了一个无界的 Future 列表，每个列表都连接到数据库 - list 中的每个条目一个。

这可以通过串行运行插入来解决，强制每个插入批处理依赖于前一个:

// Empty Future for the results. Replace Unit with the correct type - whatever
// "res" is below.
val emptyFuture = Future.successful(Seq.empty[Unit])
// This will only insert one at a time. You could use list.sliding to batch the
// inserts if that was important.
val temp1 = list.foldLeft(emptyFuture) { (previousFuture, trip) =>
  previousFuture flatMap { previous =>
    // Inner code copied from your example.
    val data = for {
      tripData <- TripDataRepository.insertQuery(trip.tripData)
      subTripData <- SubTripDataRepository.insertBatchQuery(getUpdatedSubTripDataList(trip.subTripData, tripData.id))
    } yield ((tripData, subTripData))
    val res = db.run(data.transactionally)
    previous :+ res
  }
}