Question

val enableJdbcStreaming: (java.sql.Statement) => Unit = { statement ⇒
  if (statement.isWrapperFor(classOf[com.mysql.jdbc.StatementImpl])) {
        statement.unwrap(classOf[com.mysql.jdbc.StatementImpl]).enableStreamingResults()
  }
}

implicit val actorSystem = ActorSystem()
implicit val actorMaterializer = ActorMaterializer()
val config = ConfigFactory.load()
val db = Database.forConfig("mysql")
val query = Tables.Foo.map(r => (r.id, r.pid)).result
val source = Source.fromPublisher[(Long, Option[Long])](db.stream(query.withStatementParameters(statementInit = enableJdbcStreaming)))
val future = source.runForEach(x => println(x))
import actorSystem.distpatcher
future.onComplete{ _ => 
  db.close()
  actorSystem.terminate()
}
Await.result(future, Duration.Inf)
Await.result(actorsystem.whenTerminated, Duration.Inf)

库依赖

"com.lightbend.akka" %% "akka-stream-alpakka-cassandra" % "0.11",
"com.typesafe.slick" %% "slick" % "3.2.1",
"com.typesafe.slick" %% "slick-hikaricp" % "3.2.1",
"mysql" % "mysql-connector-java" % "5.1.44",
"ch.qos.logback" % "logback-classic" % "1.2.3"

mysql config

mysql {
  profile = "slick.jdbc.MySQLProfile$"
  dataSourceClass = "slick.jdbc.DatabaseUrlDataSource"
  properties {
    driver = "com.mysql.jdbc.Driver"
    url  = "jdbc:mysql://server:3306/db"
    user = "user"
    password = "password"
  }
  connectionTimeout = 300
}

当我运行此代码时。它只是在控制台上打印这些行

[info] 19:20:31.647 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:21:01.649 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:21:31.656 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:22:01.661 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:22:31.668 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:23:01.674 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:23:31.680 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:24:01.687 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:24:31.693 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:25:01.699 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:25:31.706 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)
[info] 19:26:01.708 [mysql housekeeper] DEBUG com.zaxxer.hikari.pool.HikariPool - mysql - Pool stats (total=21, active=1, idle=20, waiting=0)

我等了很长时间，但它继续印刷这些线条。

我的期望是它会立即开始逐行读取表格。

Answer 1

我自己解决了这个问题。我想我没有正确构建图表。

我使用RunnableGraph重写了我的图形。现在它完美无缺

val query = sql"select id from foo".as[Long]
val publisher = db.stream(query.withStatementParameters(statementInit = enableJdbcStreaming))
val source = Source.fromPublisher[Long](publisher)
val sink = Sink.foreach[Long]{x => println(x)}
val graph = RunnableGraph.fromGraph(GraphDSL.create(sink){implicit b => s =>
  import GraphDSL.Implicits._
  source ~> s.in
  ClosedShape
})
val future = graph.run()
Await.result(future, Duration.Inf)

虽然知道为什么之前的方法不起作用会很有趣。

Slick 3 MySQL Streaming应用程序只挂起......（不会流数据）

1 个答案: