Dustin Cote created HIVE-13019:
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Summary: Optimizer COLLECT_LIST/COLLECT_SET
Key: HIVE-13019
URL: https://issues.apache.org/jira/browse/HIVE-13019
Project: Hive
Issue Type: Improvement
Reporter: Dustin Cote
Priority: Minor
Currently when using a COLLECT_SET/COLLECT_LIST that involves data from a
single table, the aggregation is done after any JOIN operation that is present
in the query. For example:
{code}
insert into table nested_customers_orders
select c.*, collect_list(named_struct("oid", o.oid, "order_date": o.date...))
from customers c inner join orders o on (c.cid = o.oid)
group by o.oid, o.date,...
{code}
If we can tell the optimizer to perform the COLLECT_LIST first (where possible)
we can see some performance gains in this pattern of query.
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