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https://issues.apache.org/jira/browse/HIVE-2284?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ning Zhang updated HIVE-2284:
-----------------------------
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.
was:
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.
> bucketized map join should allow join key as a superset of bucketized columns
> -----------------------------------------------------------------------------
>
> 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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