对存储在Hive中的数据运行Pig查询 [英] Running Pig query over data stored in Hive

问题描述

我想知道如何运行以Hive格式存储的Pig查询。我配置了Hive来存储压缩数据（使用本教程 http://wiki.apache.org/的hadoop /蜂房/ CompressedStorage ）。

在此之前，我曾经使用Hive的分隔符（^ A）使用正常的Pig加载函数。但是现在Hive将数据存储在具有压缩的序列文件中。使用哪个加载函数？

请注意，不需要像这里提到的那样紧密集成：使用Hive with Pig ，使用何种加载函数来读取Hive生成的压缩序列文件。

感谢所有的答案。

解决方案

下面是我发现的：
如果将数据存储为RCFile，则使用HiveColumnarLoader是有意义的。要使用此方法加载表，您需要首先注册一些jar文件：

  register /srv/pigs/piggybank.jar 
 register /usr/lib/hive/lib/hive-exec-0.5.0.jar 
 register /usr/lib/hive/lib/hive-common-0.5.0.jar 
 
a = LOAD'/ user / hive / warehouse / table'USING org.apache.pig.piggybank.storage.HiveColumnarLoader（'ts int，user_id int，url string'）; 
  

要从Sequence文件加载数据，您必须使用PiggyBank（如前例）。 Piggybank的SequenceFile加载器应该处理压缩文件：

  register /srv/pigs/piggybank.jar 
 DEFINE SequenceFileLoader org。 apache.pig.piggybank.storage.SequenceFileLoader（）; 
 a = LOAD'/ user / hive / warehouse / table'使用SequenceFileLoader AS（int，int）; 
  

这对Pig 0.7无效，因为它无法读取BytesWritable类型并将其转换为Pig类型你得到这个异常：

  2011-07-01 10：30：08,589 WARN org.apache.pig.piggybank.storage .SequenceFileLoader：无法将key类org.apache.hadoop.io.BytesWritable转换为Pig数据类型
 2011-07-01 10：30：08,625 WARN org.apache.hadoop.mapred.Child：运行child的错误
 org.apache.pig.backend.BackendException：错误0：无法将类org.apache.hadoop.io.BytesWritable转换为org.apache.pig.piggybank.storage.SequenceFileLoader中的Pig数据类型
。 setKeyType（SequenceFileLoader.java:78）
 at org.apache.pig.piggybank.storage.SequenceFileLoader.getNext（SequenceFileLoader.java:132）
 at org.apache.pig.backend.hadoop.executionengine。 mapReduceLayer.PigRecordReader.nextKeyValue（PigRecordReader.java:142）
 at org.apache.hadoop.mapred.MapTask $ NewTrackingRecordReader.nextKeyValue（MapTas 
 at org.apache.hadoop.mapreduce.Mapper.run（Mapper.java：k.java:448）
 at org.apache.hadoop.mapreduce.MapContext.nextKeyValue（MapContext.java:67）
 at org.apache.hadoop.mapreduce.Mapper.run（Mapper.java： 
 at org.apache.hadoop.mapred.MapTask.runNewMapper（MapTask.java:639）
 at org.apache.hadoop.mapred.MapTask.run（MapTask.java:315）
 at org.apache.hadoop.mapred.Child $ 4.run（Child.java:217）$ b $ 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:1063）
 at org.apache.hadoop.mapred.Child.main（Child .java：211）
  

如何编译piggybank在这里描述：无法建立piggybank - > / home / build / ivy / lib不存在

I would like to know how to run Pig queries stored in Hive format. I have configured Hive to store compressed data (using this tutorial http://wiki.apache.org/hadoop/Hive/CompressedStorage).

Before that I used to just use normal Pig load function with Hive's delimiter (^A). But now Hive stores data in sequence files with compression. Which load function to use?

Note that don't need close integration like mentioned here: Using Hive with Pig, just what load function to use to read compressed sequence files generated by Hive.

Thanks for all the answers.

解决方案

Here's what I found out: Using HiveColumnarLoader makes sense if you store data as a RCFile. To load table using this you need to register some jars first:

register /srv/pigs/piggybank.jar
register /usr/lib/hive/lib/hive-exec-0.5.0.jar
register /usr/lib/hive/lib/hive-common-0.5.0.jar

a = LOAD '/user/hive/warehouse/table' USING org.apache.pig.piggybank.storage.HiveColumnarLoader('ts int, user_id int, url string');

To load data from Sequence file you have to use PiggyBank (as in previous example). SequenceFile loader from Piggybank should handle compressed files:

register /srv/pigs/piggybank.jar
DEFINE SequenceFileLoader org.apache.pig.piggybank.storage.SequenceFileLoader();
a = LOAD '/user/hive/warehouse/table' USING SequenceFileLoader AS (int, int);

This doesn't work with Pig 0.7 because it's unable to read BytesWritable type and cast it to Pig type and you get this exception:

2011-07-01 10:30:08,589 WARN org.apache.pig.piggybank.storage.SequenceFileLoader: Unable to translate key class org.apache.hadoop.io.BytesWritable to a Pig datatype
2011-07-01 10:30:08,625 WARN org.apache.hadoop.mapred.Child: Error running child
org.apache.pig.backend.BackendException: ERROR 0: Unable to translate class org.apache.hadoop.io.BytesWritable to a Pig datatype
    at org.apache.pig.piggybank.storage.SequenceFileLoader.setKeyType(SequenceFileLoader.java:78)
    at org.apache.pig.piggybank.storage.SequenceFileLoader.getNext(SequenceFileLoader.java:132)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigRecordReader.nextKeyValue(PigRecordReader.java:142)
    at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.nextKeyValue(MapTask.java:448)
    at org.apache.hadoop.mapreduce.MapContext.nextKeyValue(MapContext.java:67)
    at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:143)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:639)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:315)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:217)
    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:1063)
    at org.apache.hadoop.mapred.Child.main(Child.java:211)

How to compile piggybank is described here: Unable to build piggybank -> /home/build/ivy/lib does not exist

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