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From "Daniel Dai (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-1322) Logical Optimizer: change outer join into regular join
Date Mon, 22 Mar 2010 22:45:27 GMT
Logical Optimizer: change outer join into regular join
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                 Key: PIG-1322
                 URL: https://issues.apache.org/jira/browse/PIG-1322
             Project: Pig
          Issue Type: New Feature
          Components: impl
    Affects Versions: 0.7.0
            Reporter: Daniel Dai
            Assignee: Daniel Dai


In some cases, we can change the outer join into a regular join. The benefit is regular join
is easier to optimize in subsequent optimization. 

Example:
C = join A by a0 LEFT OUTER, B by b0;
D = filter C by b0 > 0;

=> 
C = join A by a0, B by b0;
D = filter C by b0 > 0;

Because we made this change, so PushUpFilter rule can further push the filter in front of
regular join which otherwise cannot.

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