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Hadoop >> mail # user >> has bzip2 compression been deprecated?


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Tony Burton 2012-01-09, 13:47
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Harsh J 2012-01-09, 15:34
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RE: has bzip2 compression been deprecated?
Thanks for the quick reply and the clarification about the documentation.

Regarding sequence files: am I right in thinking that they're a good choice for intermediate steps in chained MR jobs, or for file transfer between the Map and the Reduce phases of a job; but they shouldn't be used for human-readable files at the end of one or more MapReduce jobs? How about if the only use a job's output is analysis via Hive - can Hive create tables from sequence files?

Tony

-----Original Message-----
From: Harsh J [mailto:[EMAIL PROTECTED]]
Sent: 09 January 2012 15:34
To: [EMAIL PROTECTED]
Subject: Re: has bzip2 compression been deprecated?

Bzip2 is pretty slow. You probably do not want to use it, even if it does file splits (a feature not available in the stable line of 0.20.x/1.x, but available in 0.22+).

To answer your question though, bzip2 was removed from that document cause it isn't a native library (its pure Java). I think bzip2 was added earlier due to an oversight, as even 0.20 did not have a native bzip2 library. This change in docs does not mean that BZip2 is deprecated -- it is still fully supported and available in the trunk as well. See https://issues.apache.org/jira/browse/HADOOP-6292 for the doc update changes that led to this.

The best way would be to use either:

(a) Hadoop sequence files with any compression codec of choice (best would be lzo, gz, maybe even snappy). This file format is built for HDFS and MR and is splittable. Another choice would be Avro DataFiles from the Apache Avro project.
(b) LZO codecs for Hadoop, via https://github.com/toddlipcon/hadoop-lzo (and hadoop-lzo-packager for packages). This requires you to run indexing operations before the .lzo can be made splittable, but works great with this extra step added.

On 09-Jan-2012, at 7:17 PM, Tony Burton wrote:

> Hi,
>
> I'm trying to work out which compression algorithm I should be using in my MapReduce jobs.  It seems to me that the best solution is a compromise between speed, efficiency and splittability. The only compression algorithm to handle file splits (according to Hadoop: The Definitive Guide 2nd edition p78 etc) is bzip2, at the expense of compression speed.
>
> However, I see from the documentation at http://hadoop.apache.org/common/docs/current/native_libraries.html that the bzip2 library is no longer mentioned, and hasn't been since version 0.20.0, see http://hadoop.apache.org/common/docs/r0.20.0/native_libraries.html - however the bzip2 Codec is still in the API at http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/io/compress/BZip2Codec.html.
>
> Has bzip2 support been removed from Hadoop, or will it be removed soon?
>
> Thanks,
>
> Tony
>
>
>
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Harsh J 2012-01-09, 16:49
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alo.alt 2012-01-09, 17:02
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Bejoy Ks 2012-01-09, 17:33
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Tony Burton 2012-01-09, 18:02
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Bejoy Ks 2012-01-09, 18:59
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Tony Burton 2012-01-10, 11:08
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Joey Echeverria 2012-01-10, 11:27
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Tim Broberg 2012-01-09, 20:27
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bejoy.hadoop@... 2012-01-09, 21:22
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Tim Broberg 2012-01-09, 21:42
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Tim Broberg 2012-01-09, 22:39
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Tony Burton 2012-01-10, 10:48
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Harsh J 2012-01-10, 11:42
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Bejoy Ks 2012-01-10, 18:01