Krisztian Kasa created HIVE-26524:
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Summary: Use Calcite to remove sections of a query plan known
never produces rows
Key: HIVE-26524
URL: https://issues.apache.org/jira/browse/HIVE-26524
Project: Hive
Issue Type: Improvement
Components: CBO
Reporter: Krisztian Kasa
Assignee: Krisztian Kasa
Calcite has a set of rules to remove sections of a query plan known never
produces any rows. In some cases the whole plan can be removed. Such plans are
represented with a single {{Values}} operators with no tuples. ex.:
{code}
select y + 1 from (select a1 y, b1 z from t1 where b1 > 10) q WHERE 1=0
{code}
{code}
HiveValues(tuples=[[]])
{code}
Other cases when plan has outer join or set operators some branches can be
replaced with empty values moving forward the join/set operator can be removed
{code}
select a2, b2 from t2 where 1=0
union
select a1, b1 from t1
{code}
{code}
HiveAggregate(group=[{0, 1}])
HiveTableScan(table=[[default, t1]], table:alias=[t1])
{code}
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