Eric Hanson created HIVE-4701:
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Summary: Optimize filter Column IN ( list-of-constants ) for
vectorized execution
Key: HIVE-4701
URL: https://issues.apache.org/jira/browse/HIVE-4701
Project: Hive
Issue Type: Sub-task
Reporter: Eric Hanson
OR filters have been optimized to run with vectorized query execution. IN
filters of the form "Column IN (list-of-constants)" are a special case of OR.
However, IN does not vectorized currently.
E.g.
select ddate, count(*) from factsqlengineam_vec_orc where ddate = "2012-05-19
00:00:00" OR ddate = "2012-05-20 00:00:00" or ddate = "2012-05-21 00:00:00"
group by ddate;
takes about 23 seconds of CPU and
select ddate, count(*) from factsqlengineam_vec_orc where ddate IN ("2012-05-19
00:00:00", "2012-05-20 00:00:00", "2012-05-21 00:00:00") group by ddate;
takes about 153 seconds of CPU.
A simple fix may be that for short IN lists (say <= 64 elements) we turn them
into OR by manipulating the query tree before planning whether vectorization
can be used.
A more complex fix that covers more cases would be to turn longer IN lists into
a join so when we eventually support vectorized joins it will be fast.
An intermediate approach might be to implement a special IN filter operator
that stores the constant values in a sorted array or high-performance hash
table (like Cuckoo hashing).
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