Details
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Improvement
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Status: Closed
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Major
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Resolution: Fixed
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None
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None
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None
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Reviewed
Description
Currently bucketized mapjoin only allow the join keys being exactly the same as bucketized columns. This is too restrictive and is missing some optimization opportunities.
If tables S and T are both bucketized on column A with the same # of buckets, and the query is something like:
<code>
SELECT /*+ MAPJOIN (S) */ ...
FROM S join T
ON (S.A = T.A AND S.B = T.B)
<code>
We should allow bucketized mapjoin since it's straightforward that bucket 1 from S join with bucket 2 from T on such join condition must be empty.