bucketized map join should allow join key as a superset of bucketized columns
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Key: HIVE-2284
URL: https://issues.apache.org/jira/browse/HIVE-2284
Project: Hive
Issue Type: Improvement
Reporter: Ning Zhang
Assignee: Ning Zhang
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.
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