chris schrader created HIVE-6942:
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             Summary: Explanation of GROUPING__ID is confusing
                 Key: HIVE-6942
                 URL: https://issues.apache.org/jira/browse/HIVE-6942
             Project: Hive
          Issue Type: Improvement
          Components: Documentation
            Reporter: chris schrader
            Priority: Minor


The explanation given for GROUPING__ID in enhanced aggregations is very 
incomplete and confusing based on the example.  Documentation here: 

https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation,+Cube,+Grouping+and+Rollup#EnhancedAggregation,Cube,GroupingandRollup-Grouping__IDfunction

It would be far easier to understand if the "bit vector" were explained better 
along side the examples given.  IE, also explain identifying each column in 
terms of the binary number it returns and then show it converted to decimal.  
In the examples provided, the binary equivalent of the grouping ID's for the 
first example would be 1,11,11 representing the columns included in 
aggregation.  The documentation is very confusing without this clear connection 
between creating a binary number that gets converted (just referring to it as a 
"bitvector" isn't sufficient to the average user).



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