Vineet Garg created HIVE-20826:
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Summary: Enhance HiveSemiJoin rule to convert join + group by on
left side to Left Semi Join
Key: HIVE-20826
URL: https://issues.apache.org/jira/browse/HIVE-20826
Project: Hive
Issue Type: Improvement
Reporter: Vineet Garg
Assignee: Vineet Garg
Currently HiveSemiJoin rule looks for pattern where group by is on right side.
We can convert joins which have group by on left side (assuming group by keys
are same as join keys and none of the columns are being projected from left
side) to LEFT SEMI JOIN by swapping the inputs. e.g. queries such as:
{code:sql}
explain select pp.p_partkey from (select distinct p_name from part) p join part
pp on pp.p_name = p.p_name;
{code}
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