Question

我是Pig的新手，我正在尝试在我们的5节点hadoop集群上运行以下PigScript。以下脚本为我提供了关系中两列的集合交集

register '/home/workspace/Pig/setIntersecUdf.jar'; 
define Inter com.cs.pig.SetIntersection(); 
a = load '/home/pig/pig-0.12.0/input/location.txt' as (location:chararray); 
b = load '/home/pig/pig-0.12.0/input/location.txt' as (location:chararray); 
c = CROSS a,b parallel 10; 
c = DISTINCT c; 
d = Foreach c generate $0,$1,Inter($0,$1) as intersection; 
e = Filter d by intersection !='[]' parallel 10; 
e = Filter e by $0!=$1 parallel 10; 
Store e into '/home/Documents/Pig_output';

我有一个6 Mb的文件，其中包含san diego CA或san d CA等地点。我希望第三列是两者的交集，即[san，CA]。我有这个文件有321,372条记录，并且必须自带一个CROSS以获得两列，这样我就可以一次处理每个元组。

正如我所指出的那样，他的6 Mb文件转换为大约1.9 Tb，因此，由于磁盘空间不足，我的工作失败了。

我可以对此脚本进行哪些更改以使其高效运行？

以下是我得到的错误：

Java.io.IOException: org.apache.hadoop.ipc.RemoteException: java.io.IOException: File /tmp/temp-10926921/tmp-1823693600/_temporary/_attempt_201401171541_0001_r_000000_0/part-r-00000 could only be replicated to 0 nodes, instead of 1
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:1639) 
at  org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:736)
at sun.reflect.GeneratedMethodAccessor29.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:578)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1393)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1389)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1387)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.runPipeline(PigGenericMapReduce.java:469)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.processOnePackageOutput(PigGenericMapReduce.java:432)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.reduce(PigGenericMapReduce.java:404)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapReduce$Reduce.reduce(PigGenericMapReduce.java:256)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:176)
at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:650)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:418)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149)
at org.apache.hadoop.mapred.Child.main(Child.java:249) Caused by: org.apache.hadoop.ipc.RemoteException: java.io.IOException: File /tmp/temp-10926921/tmp-1823693600/_temporary/_attempt_201401171541_0001_r_000000_0/part-r-00000 could only be replicated to 0 nodes, instead of 1
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:1639)
at org.apache.hadoop.hdfs.server.namenode.NameNode.addBlock(NameNode.java:736)
at sun.reflect.GeneratedMethodAccessor29.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:578)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1393)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1389)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1387)
at org.apache.hadoop.ipc.Client.call(Client.java:1107)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:229)
at $Proxy2.addBlock(Unknown Source)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:85)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:62)
at $Proxy2.addBlock(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.locateFollowingBlock(DFSClient.java:3686)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.nextBlockOutputStream(DFSClient.java:3546)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.access$2600(DFSClient.java:2749)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream$DataStreamer.run(DFSClient.java:2989)

Answer 1

首先，DISTINCT之后的CROSS不太可能做任何事情。 DISTINCT尊重顺序，所以它只会摆脱完全相同的元组。只有在输入文件中有相同行的倍数时才会出现这种情况。

e = Filter e by $0!=$1 ...应该在找到线的交叉点之前完成。无论如何你都要扔掉它们，所以你要尽快做到这一点。

要解决此问题，您需要以某种方式限制CROSS。我不知道您的数据是什么样的，或者您期望作为输出的内容，但事先GROUP按状态数据应该减少CROSS元组的数量将会显着减少。但是，这不会返回以下内容的交集：foo CA和foo CT。

Answer 2

交叉关系导致数据量大幅增加，即使是数量级。通常有一种更有效的解决方案，这取决于数据本身。如果您可以从每个集合中添加一些记录并解释所需的输出应包含的内容，社区就能够为您提供帮助。

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2 个答案: