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From Harsha HN <>
Subject Question on MAPJOIN Vs JOIN performance
Date Thu, 16 Apr 2015 06:38:53 GMT
Hi All,

I went through below mentioned Facebook engineering page,

I set following for auto conversion of joins,
set hive.mapjoin.smalltable.filesize=1000000000;    (1GB)

I observed some queries performed 2X faster in MAP JOIN as opposed to
Common join
and also instances where MAP JOIN is 3X slower than Common Join.

Any thoughts on what might be slowing down MAP JOIN in some cases ?

I have 40 Node cluster, so I have huge RAM available.


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