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From "amareshwarisr ." <amareshw...@gmail.com>
Subject Re: JoinChain Outer Join Enhancement
Date Sat, 20 Aug 2016 04:45:23 GMT
Outer join specification is possible at query level. For the same join
chain, different users might be interested in different type of joins at
run time. So, it is not tied to join chain as such.

You can also give join type through lens.cube.query.join.type, at query
level.

Thanks

On Fri, Aug 19, 2016 at 11:07 PM, Tao Yan <tyan@linkedin.com> wrote:

> Hi Lens Developers,
>
> I am running some tests using our production data. When I create a
> JoinChain between dim_1 and dim_2, I found it always generate 'join', i.e.:
>
> ... FROM dim_1 dim1 join dim_2 dim2 on dim1.column_a = dim2.column_b
>
> If I want to generate *left outer join*, will I be able to just add a
> property in the JoinChain definition? For example:
>
>             <edge>
>               <from table="dim_1" column="column_a" *mandatory="true"*/>
>               <to table="dim_2" column="column_b" />
>             </edge>
>
> Here *mandatory="true" indicates a left outer join, the following
> indicates a right outer join:*
>
>             <edge>
>               <from table="dim_1" column="column_a"/>
>               <to table="dim_2" column="column_b" *mandatory="true"*/>
>             </edge>
>
> The source here shows that feature is currently not supported:
> http://grepcode.com/file/repo1.maven.org/maven2/org.
> apache.lens/lens-api/2.1.0-beta-incubating/org/apache/lens/api/metastore/
> XTableReference.java?av=f
>
> I found the example outer join queries here:
> https://github.com/apache/lens/blob/master/lens-
> examples/src/main/resources/dimension-queries.sql
>
> But it looks exactly the same as normal SQL, and does not leverage the
> JoinChain feature.
>
> Thanks,
> --
>
> *Tao Yan*
> Software Engineer
> Data Analytics Infrastructure Tools and Services
>
>
>
> 206.250.5345
> tyan@linkedin.com
> https://www.linkedin.com/in/taousc
>

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