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From "Darcy Benoit" <darcy.ben...@acadiau.ca>
Subject Re: paging Scott MacDonald re DERBY-396
Date Mon, 27 Feb 2006 20:34:20 GMT

	Scott was one of my students, and he was working on DERBY-396. He has since graduated and
moved on from our university. He ran into some problems with DERBY-396, which can simply be
summed up as problems with return values. When you are accessing a table to alter it, you
need to lock the table in order to keep other users from altering the table at the same time.
Once the change has been made, you can then release the lock on the table, which is essentially
a "return". This isn't a problem when you are adding columns, as there is nothing to return.
But the existing circumstance for RENAME and DROP require that the object being renamed or
dropped is returned. This results in a case where you have a return within a return - something
that doesn't work so well with Java. He tried several different ways to work around this problem,
including not returning the objects when performing RENAMEs and DROPs, returning only the
node but not the lock, and casting the node to be renamed o
dropped as the same object type as the return type. He also tried calling separate rename
or drop methods, but the object being returned was not the same type as the object type returned
by the alter table commands.

	The result on his final report was "Due to time constraints and the problems of requiring
rename and drop statements to return values inside the alter table method, I was not able
to implement the rename and drop column functionality."

	I had suggested to Scott that he release working on the feature once he had graduated until
he was able to begin working on the project again on his own time. I guess that he didn't
get around to doing that. :(

	I have a hard copy of his final report, but I can try to relay any information from it to
whoever would like to know.


> Hi Scott,
> Please forgive me for putting you on the spot by paging you in the subject line of this
message. I
> have tried to privately ping your JIRA email address (044276m@acadiau.ca
> <mailto:044276m@acadiau.ca>), but the mail bounced back.
> You graciously volunteered to work on DERBY-396. The community wants to know whether
you'll be
> able to check in some of your code for the upcoming 10.2 release. Please feel free to
ask the
> community for advice. Many people are keen to see this feature and would be delighted
to help out
> any way they can.
> Thanks,
> -Rick

Dr. Darcy Benoit

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