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From Michael Gentry <mgen...@masslight.net>
Subject Re: Update schema
Date Tue, 03 May 2011 00:48:39 GMT
I agree with Robert that it is a difficult task and you should
probably handle it in a more controlled fashion.  I haven't had a
chance to use this yet, but Flyway sounds promising to me for
automating schema updates:

http://code.google.com/p/flyway/

mrg


On Mon, May 2, 2011 at 8:28 PM, Robert Zeigler
<robert.zeigler@roxanemy.com> wrote:
> In the modeler, there are tools for migrating a database schema, so the basic functionality
exists, but...
> Migrating a db schema is inherently tricky.  If you're adding a new column... what should
be the value supplied for existing records, for instance?
> The complexity only increases from there.
> What I've done in the past is to use the the db migration tools in the modeler to generate
a set of sql updates, augmented those updates (sometimes with sql, and sometimes with code),
and then created a "db patcher" tool.  One strategy that worked reasonably well was to have
a small, unmapped table in the database that keeps track of the current "patch level" of the
db.  The tool would then find all of the unapplied patches and apply them in incremental
order.  This strategy allowed for some fairly complex schema changes (splitting data from
a table into a separate joined table, for instance) which still largely automating the process
of schema migration across multiple application installations.
>
> Robert
>
> On May 2, 2011, at 5/27:15 PM , Steve Springett wrote:
>
>> Currently I'm using CreateIfNoSchemaStrategy and it seems to work quite well
>> for the database platforms I'm targeting.
>>
>> My question is, is there any way or examples somewhere to update the schema
>> if it's different?  For example, if the map contains an additional field,
>> table or index I would like Cayenne to be able to create the field, table or
>> index to match what is in the map. This would occur on startup for example
>> during a product update.
>>
>>
>> --Steve
>
>

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