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From Stephan Ewen <se...@apache.org>
Subject Re: Need some help to implement the outer join operator
Date Sat, 13 Dec 2014 15:25:57 GMT
Hi Wilson!

You can start by mocking an outer join operator using a special CoGroup
function. If one of the two sides for a group is empty, you have the case
where you need to append null values. Otherwise, you build the Cartesian
produce within the group.

For a proper through-the-stack implementation (not sure if that is needed,
but may be nice to have), have a look here:

http://flink.incubator.apache.org/docs/0.7-incubating/internal_add_operator.html

Greetings,
Stephan


On Sat, Dec 13, 2014 at 3:19 AM, Zihong Cao <wilsoncao01@gmail.com> wrote:
>
> Hi,
>
> I am trying to pick up the outer join operator. However, as Fabian
> mentioned to me, that this task would require to touch many different
> components of the system, it would be a challenge job for me. Therefore I
> would need some help:-)
>
> I might need to walk through some features like Compiler/Optimizer and
> Runtime(as Fabian mentioned to me), so where should I start to get familiar?
>
> One more thing, is the outer join operator implementation similar to the
> pure join operator?
>
> Best,
> Wilson Cao

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