Optimize map-side scans for right-side of join
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Key: HIVE-2116
URL: https://issues.apache.org/jira/browse/HIVE-2116
Project: Hive
Issue Type: Improvement
Reporter: Ron Bodkin
I had a large query like select * from a join b on a.key=b.key where...;
Table b was too large, so I attempted to optimize by adding constraints on b to
the where clause, e.g.,
where b.size>=mn and b.size<=mx and ...;
However, the Hive 0.8.0 optimizer pushed the constraint on b into the reduce
phase (defeating its purpose).
I was able to force Hive to run the optimization map-side by this workaround:
join (select * from b where size>=mn and size<=mx) b on a.key=b.key where ...;
But it would be nice for Hive to pull filters on joined records into the map
phase where possible.
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