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From "Jerry Chen (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-9996) Improve TFile format to support any compression codecs
Date Thu, 26 Sep 2013 06:12:02 GMT
Jerry Chen created HADOOP-9996:

             Summary: Improve TFile format to support any compression codecs
                 Key: HADOOP-9996
                 URL: https://issues.apache.org/jira/browse/HADOOP-9996
             Project: Hadoop Common
          Issue Type: Improvement
          Components: io
    Affects Versions: 3.0.0
            Reporter: Jerry Chen

TFile is a container of key-value pairs. It supports block level compression by using compression
codec. But one limitation of the current implementation is it supports only a few of fixed
compression codecs. They are LZO, GZ or no compression. Some new compression codecs such as
Snappy cannot be used because of this limitation.

We propose to extend the existing TFile compression feature to support any compression codecs.
As TFile already used the named compression codecs and stored the name in the file meta data
(for example, “lzo” was stored when LZO compression is used), we cannot change this for
backward compatibility. To make it support any compression codec, we add a special name “codec”
after which follows the real codec class name. For example, “codec: org.apache.hadoop.io.compress.SnappyCodec”
is used and stored in the meta when SnappyCodec is used as the compression codec. We can still
use the existing fixed names such as “lzo”, “gz” or “none” for specifying the
TFile compression codec.


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