Handling migrations with multiple databases in Rails

Rails
1

I have a Rails reporting application that will generate reports for
other Rails applications.

As such I need to import legacy databases, but might also over time,
change them.

How do I handle migrations with having, and connecting to, x number of
databases?

I’ve defined the ‘other’ databases connections in my classes:

class OtherApp < ActiveRecord::Base
self.abstract_class = true
establish_connection :otherApp1_development # defined in database.yml

def initialize
self.establish_connection
end
end

Yet when I use:

class CreateApplicationExampleOne < OtherApp
def self.up
# definitions etc
end
end

and then try to migrate, it fails.

I hope I’m missing something small here.

2

On 3 Jan 2011, at 13:18, Sem P. [email protected] wrote:

I have a Rails reporting application that will generate reports for
other Rails applications.

As such I need to import legacy databases, but might also over time,
change them.

How do I handle migrations with having, and connecting to, x number of
databases?

You’d want to establish_connection on ActiveRecord::Base, since that’s
what create_table etc will use. I’m not sure what will happen with your
schema_migrations table (which is how it determines what migrations to
one), out of the box rails will always look at your primary database for
this. You might find it easier to define a rails env for each of these
databases and then run migrate for each such environment.

Fred

3

Thanks. It does seem like multiple DBs and migrations do not necessarily
play well.

Would be interesting to see a recipe for this somewhere.

Frederick C. wrote in post #972014:

You might find it easier to define a rails env for each of these
databases and then run migrate for each such environment.

Fred