[
https://issues.apache.org/jira/browse/HADOOP-2120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13168554#comment-13168554
]
Ari Pollak commented on HADOOP-2120:
------------------------------------
Even if the copyMerge comment is somewhat correct, the documentation for fs
-getMerge is still confusing, so I think that this bug should be reopened; from
copyCommands.java:
public static final String DESCRIPTION =
"Get all the files in the directories that\n" +
"match the source file pattern and merge and sort them to only\n" +
"one file on local fs. <src> is kept.";
The command neither sorts nor merges the actual source files according to the
traditional definition (e.g. sort and sort -m commands), it merely concatenates
them, in order of the filenames. It should look more like this:
Concatenate all the files in the directories that match the pattern in <src>
and output to only one file on local fs. <src> is kept.
> dfs -getMerge does not do what it says it does
> ----------------------------------------------
>
> Key: HADOOP-2120
> URL: https://issues.apache.org/jira/browse/HADOOP-2120
> Project: Hadoop Common
> Issue Type: Bug
> Components: documentation, fs
> Affects Versions: 0.14.3
> Environment: All
> Reporter: Milind Bhandarkar
> Labels: newbie
>
> dfs -getMerge, which calls FileUtil.CopyMerge, contains this javadoc:
> {code}
> Get all the files in the directories that match the source file pattern
> * and merge and sort them to only one file on local fs
> * srcf is kept.
> {code}
> However, it only concatenates the set of input files, rather than merging
> them in sorted order.
> Ideally, the copyMerge should be equivalent to a map-reduce job with
> IdentityMapper and IdentityReducer with numReducers = 1. However, not having
> to run this as a map-reduce job has some advantages, since it increases
> cluster utilization during reduce phase.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
