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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