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On Wed, May 01, 2013, Ryan Lane <rlane at wikimedia.org> wrote:
> essex -> folsom and folsom -> grizzly schema changes will be the same
> forever. They never need to change. Just because we don't want to support
> essex -> grizzly upgrades, doesn't mean we need to actively remove things
> that will continue to work forever.
> 
> Obviously people are going to have to change their config files and they
> may need to replace entire services, but we should have data migration
> paths going back forever. All we have to do for this is leave them alone.

You make this sound simpler than it really is.

Ultimately there is overhead to maintain extra code, including the
migrations. Especially in the future when the new database migration code
that has been discussed is ready.

Right now that time frame is ~6 months because that is how often
releases are made.

JE