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From Stephan Ewen <se...@apache.org>
Subject Re: Left outer join
Date Wed, 15 Apr 2015 09:01:25 GMT
I think this may be a great example to add as a utility function.

Or actually add as an function to the DataSet, internally realized as a
special case of coGroup.

We do not have a ready example of that, but it should be straightforward to
realize. Similar as for the join, coGroup on the join keys. Inside the
coGroup function, emit the combination of all values from the two
iterators. If one of them is empty (the one that is not outer) then emit
all values from the outer side.

Greetings,
Stephan


On Wed, Apr 15, 2015 at 10:36 AM, Flavio Pompermaier <pompermaier@okkam.it>
wrote:

> Do you have an already working example of it? :)
>
>
> On Wed, Apr 15, 2015 at 10:32 AM, Ufuk Celebi <uce@apache.org> wrote:
>
>>
>> On 15 Apr 2015, at 10:30, Flavio Pompermaier <pompermaier@okkam.it>
>> wrote:
>>
>> >
>> > Hi to all,
>> > I have to join two datasets but I'd like to keep all data in the left
>> also if there' no right dataset.
>> > How can you achieve that in Flink? maybe I should use coGroup?
>>
>> Yes, currently you have to implement this manually with a coGroup
>
>
>

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