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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-1574) Optimization rule PushUpFilter causes filter to be pushed up out joins
Date Fri, 27 Aug 2010 18:44:54 GMT
Optimization rule PushUpFilter causes filter to be pushed up out joins
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                 Key: PIG-1574
                 URL: https://issues.apache.org/jira/browse/PIG-1574
             Project: Pig
          Issue Type: Bug
            Reporter: Xuefu Zhang
            Assignee: Xuefu Zhang
             Fix For: 0.8.0


The PushUpFilter optimization rule in the new logical plan moves the filter up to one of the
join branch. It does this aggressively by find an operator that has all the projection UIDs.
However, it didn't consider that the found operator might be another join. If that join is
outer, then we cannot simply move the filter to one of its branches.

As an example, the following script will be erroneously optimized:

        A = load 'myfile' as (d1:int);
        B = load 'anotherfile' as (d2:int);
        C = join A by d1 full outer, B by d2;        
        D = load 'xxx' as (d3:int);
        E = join C by d1, D by d3;        
        F = filter E by d1 > 5;
        G = store F into 'dummy';


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