分区键部件URL的空值无效

我有以下代码尝试在spark中加入2个cassandra表 .

val imageKeywords = sc.cassandraTable[ImageMetadata]("images", "metadata")
 val imageAndPageKeywords = imageKeywords
  .joinWithCassandraTable[PagesMetadata]("pages2", "metadata")
  .on(SomeColumns("tid", "url" as "pu"))

我用来映射数据的案例类如下

case class ImageMetadata(tid: String, iu: String, pu: Option[String],
mk: List[String], fk: List[String], ak: List[String], ipk: List[String], pk: List[String], ik: List[String], ck: List[String])

case class PagesMetadata(tid: String, url: String, pk: List[String], uk: List[String], hk: List[String], ok: List[String], tc: List[String])

当我尝试执行如下操作时，我收到错误

imageAndPageKeywords.collect.toList.sortBy(_._1.tid).take(10).foreach(println)

错误堆栈跟踪 -

引起：com.datastax.driver.core.exceptions.InvalidQueryException：com.datastax.driver.core.Responses com.datastax上的分区键部件url的无效空值 . $ Error.asException（Responses.java:103） . driver.core.DefaultResultSetFuture.onSet（DefaultResultSetFuture.java:140）在com.datastax.driver.core.RequestHandler.setFinalResult（RequestHandler.java:293）在com.datastax.driver.core.RequestHandler.onSet（RequestHandler.java： 455）位于org.jboss.netty.handler的org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream（SimpleChannelUpstreamHandler.java:70）的com.datastax.driver.core.Connection $ Dispatcher.messageReceived（Connection.java:734） .timeout.IdleStateAwareChannelUpstreamHandler.handleUpstream（IdleStateAwareChannelUpstreamHandler.java:36）org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream（DefaultChannelPipeline.java:564）org.jboss.netty.channel.DefaultChannelPipeline $ DefaultChannelHandlerContext.sendUpstream（DefaultChannelPipeline.java） ：791）在org.jb oss.netty.handler.timeout.IdleStateHandler.messageReceived（IdleStateHandler.java:294）在org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream（SimpleChannelUpstreamHandler.java:70）在org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream（ DefaultChannelPipeline.java:564）在org.jboss.netty.channel.DefaultChannelPipeline $ DefaultChannelHandlerContext.sendUpstream（DefaultChannelPipeline.java:791）在org.jboss.netty.channel.Channels.fireMessageReceived（Channels.java:296）在org.jboss .netty.handler.codec.oneone.OneToOneDecoder.handleUpstream（OneToOneDecoder.java:70）在org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream（DefaultChannelPipeline.java:564）在org.jboss.netty.channel.DefaultChannelPipeline $ DefaultChannelHandlerContext .sendUpstream（DefaultChannelPipeline.java:791）在org.jboss.netty.channel.Channels.fireMessageReceived（Channels.java:296）在org.jboss.netty.handler.codec.frame.FrameDecoder.unfoldAndFireMessageReceived（FrameDecoder.java:462 ）org.jboss . netm.handler.codec.frame.FrameDecoder.callDecode（FrameDecoder.java:443）位于org.jboss.netty.channel的org.jboss.netty.handler.codec.frame.FrameDecoder.messageReceived（FrameDecoder.java:303） . SimpleChannelUpstreamHandler.handleUpstream（SimpleChannelUpstreamHandler.java:70）在org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream（DefaultChannelPipeline.java:564）在org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream（DefaultChannelPipeline.java:559）在组织位于org.jboss.netty.channel.socket.nio.NioWorker的org.jboss.netty.channel.Channels.fireMessageReceived（Channels.java:255）的.jboss.netty.channel.Channels.fireMessageReceived（Channels.java:268） .read（NioWorker.java:88）org.jboss.netty.channel.socket.nio.AbstractNioWorker.process（AbstractNioWorker.java:108）org.jboss.netty.channel.socket.nio.AbstractNioSelector.run（AbstractNioSelector） .java：318）org.jboss.netty.channel.socket.nio.AbstractNioWorker.run（AbstractNioWorker.java:89）org.jboss.netty.channel.socket.nio.NioW orker.run（NioWorker.java:178）org.jboss.netty.util.ThreadRenamingRunnable.run（ThreadRenamingRunnable.java:108）org.jboss.netty.util.internal.DeadLockProofWorker $ 1.run（DeadLockProofWorker.java:42 ）...还有3个