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From "Napoleon Esmundo C. Ramirez" <>
Subject Re: Database compatibility checking step during startup
Date Wed, 19 Nov 2008 06:08:45 GMT
On Wed, Nov 19, 2008 at 12:28 PM, Brett Porter <> wrote:

> There's actually a version tracked in the modello metadata database table
> for this purpose already.
> The tricky part is how to do the conversion - that seems to need to be done
> outside of modello because of the complexity of having multiple versions
> (see what it did to the data management :) I think if you init normally, but
> don't load any data, then check that table for the right version, you can
> decide to upgrade it before loading any data. You'll need to lock the store
> accesses while that occurs. I expect we'd use some other migration tool like
> has been discussed recently for the task.
> - Brett
> --
> Brett Porter
I saw a ContinuumModelloMetadata class in the package.jdo file, but it isn't
declared as a table thus isn't persisted in the database.  I verified it
with a MySQL database, and that version table indeed isn't there.

The conversion is the real hard part, and I agree it is the job of the
migration tool.  I was thinking the compatibility checking step can be used
to just identify discrepancies when switching databases and to act as some
fail secure mechanism when starting continuum.  It seems that the
initialization of the database will load the data at the same time, so I was
suggesting to defer it until after the schema validation is done.

- Nap

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