Gopal Vijayaraghavan created HIVE-25589:
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Summary: SQL: Implement HAVING/QUALIFY predicates for
ROW_NUMBER()=1
Key: HIVE-25589
URL: https://issues.apache.org/jira/browse/HIVE-25589
Project: Hive
Issue Type: Improvement
Components: CBO, SQL
Affects Versions: 4.0.0
Reporter: Gopal Vijayaraghavan
The insert queries which use a row_num()=1 function are inconvenient to write
or port from an existing workload, because there is no easy way to ignore a
column in this pattern.
{code}
INSERT INTO main_table
SELECT * from duplicated_table
QUALIFY ROW_NUMER() OVER (PARTITION BY event_id) = 1;
{code}
needs to be rewritten into
{code}
INSERT INTO main_table
select event_id, event_ts, event_attribute, event_metric1, event_metric2,
event_metric3, event_metric4, .., event_metric43 from
(select *, ROW_NUMBER() OVER (PARTITION BY event_id) as rnum from
duplicated_table)
where rnum=1;
{code}
This is a time-consuming and error-prone rewrite (dealing with a messed up
order of columns between one source and dest table).
An alternate rewrite would be to do the same or similar syntax using HAVING.
{code}
INSERT INTO main_table
SELECT * from duplicated_table
HAVING ROW_NUMER() OVER (PARTITION BY event_id) = 1;
{code}
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