Question

我正在跑猪

example$ pig --version
Apache Pig version 0.8.1-cdh3u1 (rexported) 
compiled Jul 18 2011, 08:29:40

非常简单的数据集

example$ hadoop fs -cat /user/pavel/trivial.log
1   one
2   two
3   three

我正在尝试使用以下脚本将包格式保存为json：

REGISTER ./pig.jar;
A = LOAD 'trivial.log' USING PigStorage('\t') AS (mynum: int, mynumstr: chararray);
B = GROUP A BY mynum;
DUMP B;
STORE B into 'trivial_json.out' USING JsonStorage();

我收到一个错误：后端错误消息

---------------------
java.lang.NullPointerException
    at org.apache.pig.ResourceSchema.<init>(ResourceSchema.java:239)
    at org.apache.pig.builtin.JsonStorage.prepareToWrite(JsonStorage.java:129)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigOutputFormat$PigRecordWriter.<init>(PigOutputFormat.java:124)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigOutputFormat.getRecordWriter(PigOutputFormat.java:85)
    at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:559)
    at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:414)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:270)
    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:1127)
    at org.apache.hadoop.mapred.Child.main(Child.java:264)

Pig Stack Trace
---------------
ERROR 2997: Unable to recreate exception from backed error: java.lang.NullPointerException

org.apache.pig.backend.executionengine.ExecException: ERROR 2997: Unable to recreate exception from backed error: java.lang.NullPointerException
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.Launcher.getErrorMessages(Launcher.java:221)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.Launcher.getStats(Launcher.java:154)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher.launchPig(MapReduceLauncher.java:337)
    at org.apache.pig.backend.hadoop.executionengine.HExecutionEngine.execute(HExecutionEngine.java:382)
    at org.apache.pig.PigServer.executeCompiledLogicalPlan(PigServer.java:1209)
    at org.apache.pig.PigServer.execute(PigServer.java:1201)
    at org.apache.pig.PigServer.access$100(PigServer.java:129)
    at org.apache.pig.PigServer$Graph.execute(PigServer.java:1528)
    at org.apache.pig.PigServer.executeBatchEx(PigServer.java:373)
    at org.apache.pig.PigServer.executeBatch(PigServer.java:340)
    at org.apache.pig.tools.grunt.GruntParser.executeBatch(GruntParser.java:115)
    at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:172)
    at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:144)
    at org.apache.pig.tools.grunt.Grunt.exec(Grunt.java:90)
    at org.apache.pig.Main.run(Main.java:396)
    at org.apache.pig.Main.main(Main.java:107)
================================================================================

我在Java中不够强大，无法在几分钟内进行调试，有人可能会建议可能发生的事情吗？

非常感谢！ -Pavel

Answer 1

通过电子邮件对此有一些疑问，认为这可能对其他人有用：

原来，我的Pig安装中没有包含JsonStorage类。实际上它还没有出现在稳定的分支中，你不会在0.9.2中找到它。但是如果你得到最新的主干

http://svn.apache.org/repos/asf/pig/trunk/

然后trunk / test / org / apache / pig / test / TestJsonLoaderStorage.java显示它是如何工作的。如果你不反对未发布的版本，那么你可以尝试一下。如果你这样做，你还应该看看Avro（带有json元数据的二进制格式）。它也没有正式出局。

我正在尝试运行流式python作业，并试图避免手动指定架构。我最后通过猪袋并手工解析它们。

希望这会有所帮助。 -Pavel

如何以json格式保存猪包

1 个答案: