如何在Hadoop 3.0中做CopyMerge？ [英] How to do CopyMerge in Hadoop 3.0?

问题描述

我知道 hadoop 版本 2.7 的 FileUtil 有 copyMerge 函数可将多个文件合并为一个新文件。

但 copyMerge在 3.0 版本中，每个API不再支持函数。

有关如何将目录中的所有文件合并到 3.0 版本的hadoop中的新单个文件的任何想法？

解决方案

FileUtil＃copyMerge方法已被删除。查看主要更改的详细信息：

https://issues.apache.org/jira/browse/HADOOP-12967

https://issues.apache.org/jira/browse/HADOOP-11392

您可以使用getmerge

用法：hadoop fs -getmerge [-nl]

源目录和目标文件作为输入，并将src中的文件连接到目标本地文件。可选地，可以将-nl设置为在每个文件的末尾添加换行符（LF）。 -skip-empty-file可以用来避免空文件中不需要的换行符。

示例：

  hadoop fs -getmerge -nl / src /opt/output.txt 
 hadoop fs -getmerge -nl /src/file1.txt /src/file2.txt / output。 txt 
  

退出代码：
成功时返回0，错误时返回非零。 p>

https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/FileSystemShell.html#getmerge

I know hadoop version 2.7's FileUtil has the copyMerge function that merges multiple files into a new one.

But the copyMerge function is no longer supported per the API in the 3.0 version.

Any ideas on how to merge all files within a directory into a new single file in the 3.0 version of hadoop?

解决方案

FileUtil#copyMerge method has been removed. See details for the major change:

https://issues.apache.org/jira/browse/HADOOP-12967

https://issues.apache.org/jira/browse/HADOOP-11392

You can use getmerge

Usage: hadoop fs -getmerge [-nl]

Takes a source directory and a destination file as input and concatenates files in src into the destination local file. Optionally -nl can be set to enable adding a newline character (LF) at the end of each file. -skip-empty-file can be used to avoid unwanted newline characters in case of empty files.

Examples:

hadoop fs -getmerge -nl /src /opt/output.txt
hadoop fs -getmerge -nl /src/file1.txt /src/file2.txt /output.txt

Exit Code: Returns 0 on success and non-zero on error.

https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/FileSystemShell.html#getmerge

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