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From Eric Emminger <e...@ericemminger.com>
Subject Re: Database schema changes: migration how to
Date Thu, 27 Mar 2003 16:52:50 GMT
Jan

> I guess I am missing the point here, if you change a relational database
> scheme, e.g. add columns, you introduce new data. It is off course
> impossible to generate new data by means of Torque or any tool.
> I guess you are referring to other changes.
> 
> Could you give an example of such a change which could be supported by
> tools because I think I am missing the point.

Well, I was assuming, perhaps incorrectly, the following example.

1. Deploy a release of your application.
2. Continue developing your app, including adding, removing, and/or 
changing some properties in your objects. This would require the 
database schema to change to store the objects.
3. Deploy new release of your app with changes from step 2.
4. Instruct tool to automatically migrate data from app in step 1 to app 
in step 3.

Theoretically, the tool could do this if it were "aware" of the changes. 
I've used some tools in the past that come close if not accomplish this.

Was that example useful?

Eric


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