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From dag.wan...@oracle.com (Dag H. Wanvik)
Subject Re: Support for FULL OUTER JOIN
Date Fri, 16 Sep 2011 13:12:21 GMT
Melaka Gunasekara <donmelaka@gmail.com> writes:

> Hi all,
>
> I'm an undergraduate form University of Moratuwa.
> I and three of my colleagues are willing to implement full outer join for
> Derby.
>
> https://issues.apache.org/jira/browse/DERBY-4832
>
> We also came across this mail.
> http://old.nabble.com/Start-with-Derby-and-Full-outer-JOIN-td31060327.html
>
> We have done following basic steps.
>
> 1. We downloaded and built the Derby source
> 2. We were able to debug the Derby code using Netbeans
> 3. Able the dumb the query plan
> 4. Looked at the source code and are in the process of understanding how the
> Left Outer join has been implemented
>  (NestedLoopLeftOuterJoinResultSet.java )
>
> We are trying to understand how Left Outer Join has being implemented and
> them implement the Full Outer Join.

You would also need to have a look at compiler, especially
HalfOuterJoinNode. The NestedLoopLeftOuterJoinResultSet that you already
looked at is part of the execution time machinery.

Note that Derby compiles queries into Java byte codes that are loaded
and executed, so there is some complexity there you need to come to
grips with. Running query compilation and execution a debugger will help
a lot.

Dag

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