Efficient way to pull data from second database?

Question

We have a primary database where all of our app resides.

But there\'s a second database (updated from an external source), that I\'d like to be able to connect to so

Answer 1

Copy/Paste:

For a single-master situation, you could define another database connection in database.yml for the read slave:

read_slave:
  adapter: postgresql
  database: read_only_production
  username: user
  password: pass
  host: read_slave_host

This database is backed by a module, which mirrors the ActiveRecord classes using this database connection:

require 'magic_multi_connections'
module ReadSlave
  establish_connection :read_slave
end

Now, all pre-existing models can be accessed through the read_slave connection by prefixing the model class with ReadSlave::.

# use the read-only connection
    @user = ReadSlave::User.find(params[:id])

    # write to the master (can't use @user.update_attributes because it would#
    try to write to the read slave)
    User.update(@user.id, :login => "new_login")