Distinct left join #10520
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Distinct left join #10520
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Signed-off-by: Jason Lowe <jlowe@nvidia.com>
Signed-off-by: Jason Lowe <jlowe@nvidia.com>
jlowe
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performance
revans2
previously approved these changes
Mar 4, 2024
revans2
approved these changes
Mar 5, 2024
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Depends on #10503 and rapidsai/cudf#15154.
Updates the left hash join code to leverage the cudf distinct left join API where the join can be performed much more quickly when it is known there are no duplicate join keys in the hash table. Unlike distinct inner join, distinct left join does not require gathering the left table.
Running this on NDS at scale factor 3K resulted in no regressions but no statistically significant improvements either, probably because there aren't enough distinct left outer joins in practice on that benchmark. Microbenchmarks show this can be up to 35% faster than a non-distinct left outer hash join.