FAQ
Generate and accept JSON as the input-output format from mappers and reducers
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Key: HADOOP-4592
URL: https://issues.apache.org/jira/browse/HADOOP-4592
Project: Hadoop Core
Issue Type: Wish
Components: contrib/hive
Reporter: Venky Iyer


set mapred.data.format=JSON;
....
MAP USING 'python filter.py'
....;

would mean that filter.py would receive a JSON formatted dictionary of the columns instead of a tab-delimited string.

{ column1: value1, column2: [1,2,3] } etc

It would in turn produce JSON.

This should be done so that the JSON is not transmitted back and forth over the network; it would be generated on the fly on the mapper node, and converted back to the standard format used (tab-delimited, I assume).

This seems like the simplest way for encoding type information in the input to mappers; it would also remove the need for silly boilerplate code that took a list of expected input column names, took the input stream, split it up, and made a dictionary of {column name: value} on every record.

Output schemas (USING '' AS ...) might also be redundant with this in place, but I'm not sure if that is doable.

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groupcommon-dev @
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postedNov 5, '08 at 9:42a
activeNov 5, '08 at 9:42a
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Venky Iyer (JIRA): 1 post

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