ActiveRecord 3.1.0 multiple databases

Question

I\'m trying to upgrade the ActiveRecord gem to the latest 3.1.0 release and seeing a lot of exceptions being raised, I think it\'s due to how we handle multiple databases.

Answer 1

I ran into the same issue yesterday while upgrading to ActiveRecord 3.1.0. I can't speak to whether there is a new recommended way of handling multiple database connections in ActiveRecord 3.1, but I did find a way to unblock myself.

It appears a connection must now be established on ActiveRecord::Base in order for it to determine the table name lengths/rules of the adapter. Along with the rest of my connections established in my database initializer, I now also have an ActiveRecord::Base connection established to one of my DBs (it doesn't matter which one).

I'd like to think there's a better solution to be found, but I'm happy to be unblocked for now.

Answer 2

I am using this solution - What I was seeing was that when establish_connection was called in each of the OtherDb classes - there seemed to be alot of overhead reloading table definitions and I would randomly see issues every time the class def was reloaded.

# The idea here is to specify that a given model should use another
# database without having to change the entire inheritance hierarchy

# declare model for table in primary connection
class Bar < ActiveRecord::Base
  # assume we have logic here that we don't want to refactor into a module
  # but we do want to inherit in OtherDb::Bar
end

module Foo

  # base model in Foo namespace - uses another db
  class BaseConnection < ActiveRecord::Base
    # OtherDb::Title.database contains a db config hash
    # This would probably go in the initializers
    establish_connection OtherDb::Title.database 
  end

  # module used to override db connection
  module OtherDb::Base
    def retrieve_connection
      # connection_handler.retrieve_connection(self) #  normal behavior
      connection_handler.retrieve_connection(Foo::BaseConnection) # use db from Foo::BaseConnection
    end
  end

  # Foo::Bar is identical to ::Bar but is in another db
  class Bar < ::Bar
    extend OtherDb::Base
  end
end