Steve Armstrong created HDFS-7800:
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Summary: Improve documentation for FileSystem.concat()
Key: HDFS-7800
URL: https://issues.apache.org/jira/browse/HDFS-7800
Project: Hadoop HDFS
Issue Type: Task
Affects Versions: 2.6.0, 2.2.0
Reporter: Steve Armstrong
This is a documentation request.
[FileSystem.concat()|https://hadoop.apache.org/docs/current/api/org/apache/hadoop/fs/FileSystem.html]
says it will "Concat existing files together". It seems to be a Namenode-only
operation though, mapping the data blocks into a single file. This means:
# The destination must exist
# The destination must be non-empty
# The destination must have it's last block exactly full
# All but the last of the source files must have their last block full
# All the source file will be deleted by this operation
HDFS-6641 brought up some of these limitations, but was closed as not a
problem. I think the javadoc should be improved so it's clear this function was
never intended to work the same as a general purpose file concatenation.
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