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How |
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to |
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use |
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compression |
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with |
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Pentaho |
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MapReduce. |
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guide
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uses
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the
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Snappy
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compression
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codec
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in
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its
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examples,
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but
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you
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may
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use
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any
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compression
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codec
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you
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choose
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that
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is
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supported
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in
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Hadoop.
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The
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following
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scenarios
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are
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covered:
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- Reading
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- Compressed
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- Files
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- Writing
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- Compressed
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- Files
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- Compressing
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- Intermediate
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- Data
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Prerequisites
In order to follow along with this how-to
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guide
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you
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will
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need
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the
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following:
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- Hadoop
- Pentaho Data Integration
- Pentaho Hadoop Distribution
- Compression Codec Installed on Hadoop
Step-By-Step
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Instructions
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Reading
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Compressed
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Files
Normally there is nothing you need to do to have Pentaho MapReduce use a compressed file as the the input. Pentaho MapReduce will automatically decompress any compression codec installed on the Hadoop cluster.
Writing Compressed Files
- Start PDI on your desktop. Once it is running choose 'File' -> 'Open', browse to and select your job running Pentaho MapReduce, then click 'OK'.
- Configure the Compression Codec: Double click on the 'Pentaho MapReduce' step, switch to the 'User Defined' tab and enter the following information:
Name
Value
mapred.output.compression.codec
The compression codec to use. For example org.apache.hadoop.io.compress.SnappyCodec
mapred.output.compress
true
mapred.output.compression.type
BLOCK
- Run your job
The output from the job should be compressed using the codec you specified.
Compressing Intermediate Data
You may want to compress the intermediate data that is passed between the Pentaho Mappers and Reducers to reduce network i/o and in some cases improve performance.
- Start PDI on your desktop. Once it is running choose 'File' -> 'Open', browse to and select your job running Pentaho MapReduce, then click 'OK'.
- Configure the Compression Codec: Double click on the 'Pentaho MapReduce' step, switch to the 'User Defined' tab and enter the following information:
Name
Value
mapred.map.output.compression.codec
The compression codec to use. For example org.apache.hadoop.io.compress.SnappyCodec
mapred.compress.map.output
true
- Run your job