GitHub user zhonghaihua opened a pull request:

    https://github.com/apache/spark/pull/10128

    pull out nondeterministic expressions from Join

    Currently,`nondeterministic expressions` are only allowed in `Project` or 
`Filter`,And only when we use nondeterministic expressions in `UnaryNode` can 
be pulled out.
    
    But,Sometime in many case,we will use nondeterministic expressions to 
process `join keys` avoiding data skew.for example:
    ```
    select * 
    from tableA a 
    join 
    (select * from tableB) b 
    on upper((case when (a.brand_code is null or a.brand_code = '' ) then cast( 
(-rand() * 10000000 ) as string ) else a.brand_code end ))  = b.brand_code
    
    ```
    
    This PR introduce a mechanism to pull out nondeterministic expressions from 
`Join`,so we can use nondeterministic expression in `Join` appropriately.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/zhonghaihua/spark pulloutJoinNondeterministic

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/spark/pull/10128.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #10128
    
----
commit 6e166578a5c1a1faf260389509663ac8c71ec015
Author: zhonghaihua <793507...@qq.com>
Date:   2015-11-30T07:44:49Z

    pull out nondeterministic expressions from Join
    
    pull out nondeterministic expressions from Join
    
    pull out nondeterministic expressions from Join

----


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