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对 Hive 中存储的数据运行 Pig 查询

发布于 2024-11-02 22:42:34 字数 452 浏览 3 评论 0原文

我想知道如何运行以 Hive 格式存储的 Pig 查询。我已将 Hive 配置为存储压缩数据（使用本教程 http://wiki.apache.org/ hadoop/Hive/压缩存储）。

在此之前，我曾经只使用带有 Hive 分隔符 (^A) 的普通 Pig 加载函数。但现在 Hive 将数据存储在压缩的序列文件中。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：Using Hive with Pig，只需加载即可函数用于读取 Hive 生成的压缩序列文件。

感谢所有的答案。

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沩ん囻菔务 2024-11-09 22:42:34

这是我发现的：
如果您将数据存储为 RCFile，则使用 HiveColumnarLoader 很有意义。要使用此加载表，您需要首先注册一些 jar：

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');

要从序列文件加载数据，您必须使用 PiggyBank（如前面的示例所示）。 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' USING SequenceFileLoader AS (int, int);

这不适用于 Pig 0.7，因为它无法读取 BytesWritable 类型并将其转换为 Pig 类型，并且您会得到此异常：

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)

此处描述了如何编译 Piggybank：无法建立存钱罐-> /home/build/ivy/lib 不存在

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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