Yin Huai created HIVE-5258:
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Summary: Optimize aggregations without Group By followed by a
Cross Join
Key: HIVE-5258
URL: https://issues.apache.org/jira/browse/HIVE-5258
Project: Hive
Issue Type: Improvement
Reporter: Yin Huai
Assignee: Yin Huai
For example, we should use a single MR job to execute the following query
{code:sql}
SELECT *
FROM (SELECT tmp1.cnt1, tmp2.cnt2
FROM (SELECT count(*) as cnt1
FROM src1 x) tmp1
JOIN (SELECT count(*) as cnt2
FROM src1 y) tmp2) tmp3;
{code}
The reduce phase should have the reduce side GroupByOperators of tmp1 and tmp2,
and the JoinOperator for the cross join.
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