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From Avrilia Floratou <>
Subject Question on bucketed map join
Date Thu, 19 Jan 2012 15:53:28 GMT

I have two tables with 8 buckets each on the same key and want to join them.
I ran "explain extended" and get the plan produced by HIVE which shows that a map-side join
is a possible plan.

I then set in my script the hive.optimize.bucketmapjoin option to true and reran the "explain
extended" query. I get the exact same plans as output.

I ran the query with and without the bucketmapjoin optimization and saw no difference in the
running time.

I have the following questions:

1. Should I see sth different in the explain extended output if I set and unset the hive.optimize.bucketmapjoin

2. Should I see something different in the output of hive while running the query if again
I set and unset the hive.optimize.bucketmapjoin?

3. Is it possible that even though I set bucketmapjoin to true, Hive will still perform a
normal map-side join for some reason? How can I check if this has actually happened?

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