[hive] duplicate expression elimination for group by stage 1
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Key: HADOOP-4156
URL: https://issues.apache.org/jira/browse/HADOOP-4156
Project: Hadoop Core
Issue Type: Bug
Reporter: Namit Jain
In the first job we evaluate all the input columns + all group by clause
expressions + parameters to all the aggregation functions and do not eliminate
all the duplicates because we treat expression resolution and column resolution
differently.
Consider the following:
src(key, value)
select src.key, sum(src.value) from src group by src;
Both src.key and src.value will be added twice - one from src's row resolver
and one each from group expression and parameter. It is needed that way filter
looks at (table, column) in row resolver, whereas group by expression looks
at (", COLREF table column)
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