Aman Sinha created IMPALA-9983:
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Summary: Push limit from a top level sort onto analytic sort when
applicable
Key: IMPALA-9983
URL: https://issues.apache.org/jira/browse/IMPALA-9983
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Affects Versions: Impala 3.4.0
Reporter: Aman Sinha
Assignee: Aman Sinha
For queries of the following type:
{noformat}
select * from (select l_partkey, l_quantity,
rank() over (partition by l_partkey order by l_quantity desc) rk
from lineitem) dt
where rk <= 100
group by l_partkey, l_quantity
order by l_partkey, l_quantity, rk
limit 100
{noformat}
the limit 100 from the outer order by can be pushed down to the analytic sort
that is done below the AnalyticEval operator. The reason is there are
effectively 2 limits:
PARTITION BY l_partkey ORDER BY l_quantity LIMIT PER PARTITION 100
ORDER BY l_partkey .... LIMIT 100
and together they imply
ORDER BY l_partkey, l_quantity LIMIT 100
For the limit pushdown to work, the partition-by exprs must be a leading prefix
of the order-by exprs. Also, other qualifying conditions must be met based on
the above pattern.
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