Shant Hovsepian created IMPALA-9796:
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Summary: Support Subquery Coalescing / Subsumption / Merge
Key: IMPALA-9796
URL: https://issues.apache.org/jira/browse/IMPALA-9796
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Reporter: Shant Hovsepian
The idea tends to go by names each with their own subtle meaning. However in
general given multiple subqueries in a single query it may be possible to
combine them into a single subquery.
{code:java}
SELECT A.agg1, B.agg2 FROM (SELECT sum(price) as agg1 FROM T1) A, (SELECT
avg(price) as agg2 FROM T1) B; {code}
The above could be combined to calculate both aggregates in one pass.
{code:java}
SELECT C.agg1, C.agg2 FROM (SELECT sum(price) as agg1, avg(price) as agg2 FROM
T1) C;{code}
More complex subquery examples are possible where predicates disjunctive
predicates can be combined.
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