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From "Eyal Allweil (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DATAFU-130) Add left outer join macro described in the DataFu guide
Date Wed, 15 Nov 2017 14:58:00 GMT

    [ https://issues.apache.org/jira/browse/DATAFU-130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16253564#comment-16253564
] 

Eyal Allweil commented on DATAFU-130:
-------------------------------------

Hi [~varunu28],

Thank you for your interest! Do you have any experience with Pig?

I can't seem to assign this issue to you, but that isn't really necessary to work on it. Go
right ahead!

For setting up your environment, you should follow [this guide:|http://datafu.incubator.apache.org/community/contributing.htm]

We haven't published instructions for how to contribute Pig macros. I'll try to write a rough
draft of a guide and email it here or put it up on our wiki.
In the meantime, you can look at [count_macros.pig|https://github.com/apache/incubator-datafu/blob/master/datafu-pig/src/main/resources/datafu/count_macros.pig]
for an example of a macro file (though all you need to do is copy the macro in the Jira to
the macros directory), and [MacroTests.java|https://github.com/apache/incubator-datafu/blob/master/datafu-pig/src/test/java/datafu/test/pig/macros/MacroTests.java]
for an example of a test. You can add your test to this file, actually.

For a guide to how to prepare a patch file, you can look [here|https://cwiki.apache.org/confluence/display/DATAFU/Contributing+to+Apache+DataFu].


> 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
>              Labels: macro, newbie
>
> 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));
> }
> {noformat}
> (we would obviously want to add a test for this, too)



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