Rails - Mar 2013 - Is there a way to prevent an accidental migration from newer version of app to older one?

Imagine a rails app that has two versions that developers need to support: 
1.0 and 2.0. There are 2 database schemas: app-1, app-2.

After fixing a bunch of very important bugs in production (1.0), some 
junior developer named Bob switches the branch to 2.0 to implement a few 
features but somehow gets his app connected to the schema app-1 and does 
rake db:migrate

As I understand, in that case the app-1 schema will be migrated to 2.0. 
Considering a fact that migrations are not always reversible, Bob is in 
trouble and instead doing useful work, has to restore the db schema.

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On 3 March 2013 01:51, Anton Kuzmin
<thehappycoder-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Imagine a rails app that has two versions that developers need to support:
> 1.0 and 2.0. There are 2 database schemas: app-1, app-2.
>
> After fixing a bunch of very important bugs in production (1.0), some
junior
> developer named Bob switches the branch to 2.0 to implement a few features
> but somehow gets his app connected to the schema app-1 and does rake
> db:migrate
What do you mean by "connected to the schema app-1"?  Do you mean
connected to the wrong database or are you talking about schema.rb?
If you mean the wrong db then how?  By changing database.yml?  How
could he do that accidentally?

Colin
>
> As I understand, in that case the app-1 schema will be migrated to 2.0.
> Considering a fact that migrations are not always reversible, Bob is in
> trouble and instead doing useful work, has to restore the db schema.
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Colin Law wrote in post #1099927:
> On 3 March 2013 01:51, Anton Kuzmin
<thehappycoder-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> Imagine a rails app that has two versions that developers need to
support:
>> 1.0 and 2.0. There are 2 database schemas: app-1, app-2.
>>
>> After fixing a bunch of very important bugs in production (1.0), some
junior
>> developer named Bob switches the branch to 2.0 to implement a few
features
>> but somehow gets his app connected to the schema app-1 and does rake
>> db:migrate
>
> What do you mean by "connected to the schema app-1"?  Do you mean
> connected to the wrong database or are you talking about schema.rb?
> If you mean the wrong db then how?  By changing database.yml?  How
> could he do that accidentally?
AFAIK it''s recommended that schema.rb is version controller, but 
database.yml is not. This is how I always setup my development 
environments.

In this scenario each developer has their own version of database.yml, 
but everyone shares the same schema.rb.

In this case where you have a v1.0 branch and a v2.0 branch it would 
have to be left up to each developer to make sure their development 
database matches the schema.rb file of the branch they are current 
working on.

The easiest way I know to do this would be to reset the development 
database when switching from v1.0 to v2.0 and vise versa.

rake db:reset
rake db:seed (if necessary).
rake db:test:prepare

This will drop and recreate the development and test databases from 
schema.rb. No need to worry about irreversible migrations in this case. 
The development database will match the appropriate schema.rb regardless 
of what happened in migration history.

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