序列文件在Hadoop中 [英] Sequence Files in Hadoop

问题描述

如何生成这些序列文件？我看到一个关于序列文件链接，在这里，

How are these sequence files generated ? I saw a link about sequence file here,

http://wiki.apache.org/hadoop/SequenceFile

这些是使用默认的Java串行写的？和我如何读取序列文件？

Are these written using default Java serializer ? and How do I read a sequence file ?

推荐答案

序列文件由马preduce任务生成，并可以作为马preduce就业之间传输数据的通用格式。

Sequence files are generated by MapReduce tasks and and can be used as common format to transfer data between MapReduce jobs.

您可以通过以下方式阅读：

You can read them in the following manner:

Configuration config = new Configuration();
Path path = new Path(PATH_TO_YOUR_FILE);
SequenceFile.Reader reader = new SequenceFile.Reader(FileSystem.get(config), path, config);
WritableComparable key = (WritableComparable) reader.getKeyClass().newInstance();
Writable value = (Writable) reader.getValueClass().newInstance();
while (reader.next(key, value))
  // perform some operating
reader.close();

您也可以使用SequenceFile.Writer自行生成序列文件。

Also you can generate sequence files by yourself using SequenceFile.Writer.

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