Don't send constants from mapper to reducer for Group By queries
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Key: HIVE-757
URL: https://issues.apache.org/jira/browse/HIVE-757
Project: Hadoop Hive
Issue Type: Improvement
Reporter: Zheng Shao
Assignee: Zheng Shao
Fix For: 0.5.0
If an aggregation function takes a constant expression, we are still sending it
from mapper to reducer, but it's not necessary since we can compute the
constants on the reducer side.
This will be useful for some UDAF that have configuration parameters:
{code}
SELECT pageid, logistic_regression("-t 1.0 -b 2.0", col1, col2, col3) FROM
mytable GROUP BY pageid;
{code}
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