[jira] [Created] (DATAFU-130) Add left outer join macro described in the DataFu guide

["Eyal Allweil (JIRA)" <ji...@apache.org>]

Eyal Allweil created DATAFU-130:
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             Summary: Add left outer join macro described in the DataFu guide
                 Key: DATAFU-130
                 URL: https://issues.apache.org/jira/browse/DATAFU-130
             Project: DataFu
          Issue Type: New Feature
            Reporter: Eyal Allweil


In our [guide|http://datafu.incubator.apache.org/blog/2013/09/04/datafu-1-0.html], a macro is described for making a three-way left outer join conveniently. We can add this macro to DataFu to make it even easier to use.

The macro's code is as follows:


{noformat}
DEFINE left_outer_join(relation1, key1, relation2, key2, relation3, key3) returns joined {
  cogrouped = COGROUP $relation1 BY $key1, $relation2 BY $key2, $relation3 BY $key3;
  $joined = FOREACH cogrouped GENERATE
    FLATTEN($relation1),
    FLATTEN(EmptyBagToNullFields($relation2)),
    FLATTEN(EmptyBagToNullFields($relation3));
}

(we would obviously want to add a test for this, too)

{noformat}





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