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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-474) support compressed text files as input and output
Date Fri, 25 Aug 2006 19:03:23 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-474?page=comments#action_12430590 ] 
Doug Cutting commented on HADOOP-474:

+1, with a few questions:

Do we need io.compression.codecs if the codecs provide extensions?  If so, then what's the
point of having the codec's provide extensions?

Should the output property be instead named mapred.text.output.compression.codec?  In other
words, will we use this same property to name the codecs for other output formats, or is this
property for text files alone (in which case it should have 'text' in its name)?

> support compressed text files as input and output
> -------------------------------------------------
>                 Key: HADOOP-474
>                 URL: http://issues.apache.org/jira/browse/HADOOP-474
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.5.0
>            Reporter: Owen O'Malley
>         Assigned To: Owen O'Malley
>             Fix For: 0.6.0
> I'd like TextInputFomat and TextOutputFormat to automatically compress and uncompress
text files when they are read and written. Furthermore, I'd like to be able to use custom
compressors as defined in HADOOP-441. Therefore, I propose:
> Adding a map of compression codecs in the server config files:
> io.compression.codecs = "<suffix>=<codec class>,..."
> so the default would be something like:
> <property>
>   <name>io.compression.codecs</name>
>   <value>.gz=org.apache.hadoop.io.GZipCodec,.Z=org.apache.hadoop.io.ZipCodec</value>
>   <description>A list of file suffixes and the codecs for them.</description>
> </property>
> note that the suffix can include multiple "." so you could support suffixes like ".tar.gz",
but they are just treated as literals against the end of the filename.
> If the TextInputFormat is dealing with such a file, it:
>   1. makes a single split
>   2. decompresses automatically
> On the output side, if mapred.output.compress is true, then TextOutputFormat would use
a new property mapred.output.compression.codec that would define the codec to use to compress
the outputs,  defaulting to gzip. 

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