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From Donald McLean <dmclea...@gmail.com>
Subject Re: How would you implement a record-level versioning system with Derby and Java?
Date Thu, 09 Jul 2009 13:30:32 GMT
On Thu, Jul 9, 2009 at 9:03 AM, Alessandro Bottoni<alexbottoni@yahoo.it> wrote:
> Hi Guys,
> I'm completely new to Derby and I evaluating it as a possibile embedded
> RDBMS for a Java/Swing application that I'm goig to develop. I'm
> currently following the tutorials at IBM DeveloperWorks
> (http://tinyurl.com/6mlwpj) and I have ordered the IBM book at Amazon's
> already (http://tinyurl.com/ln3cas).
>
> I have a stimulating question for you all (I apologize if this topic has
> been discussed already):
>
> how would you implement a system to keep track of any old version of a
> record (row) of your database?
>
> I'm asking this because I need a system that will allow the user to see
> any old version of a record and to undo/redo any change with just a
> couple of mouse clicks.
>
> Any idea? Any suggestion?

Actually, this is a question that I have previously considered for a
project that I am starting.

My thought was to have an identity column (value assigned by the DBMS)
and a separate ID column. From here, you can do several different
things:

1. Have a "version" column. Use the max function to find the current
version, or make the current version -1 or something else easy to
find.
2. Use the max function on the identity column to find the latest version.
3. Have "previous" and "next" columns with the identity values of the
appropriate objects in the chain. The current version would have a
null "next".

There are probably other approaches that I haven't thought of.

> PS: No, I'm not planning to use any kind of ORM (Hibernate or similar).
> Should I?

I have used and recommend Hibernate. It simplifies things immensely
IMO, though it does have its quirks (some of which are not properly
explained by the documentation). It also works well with a number of
other DBMS (if changing is something that might happen later).
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