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From davies <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-13373] [SQL] generate sort merge join
Date Tue, 23 Feb 2016 00:21:40 GMT
Github user davies commented on the pull request:

    https://github.com/apache/spark/pull/11248#issuecomment-187448749
  
    @nongli We already avoid the copy until found the match. In order to support left N rows
match with right M rows, we have to copy some of them. Right now, we copy the keys from left,
and the rows from right. It's possible to have less copies, I'd like to leave that out of
this PR, because SMJ usually required Exchange and Sort, those are more expensive than coping
the matched rows from right.


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