gistfile1.rb

maximum_id = 0

[:customer_a, :customer_b].each do |database_name|

  ActiveRecord::Base.establish_connection(database_name)

  maximum_id_in_database = 0

  ActiveRecord::Base.connection.tables.each do |table_name|

    maximum_id_in_table = table_name.classify.constantize.maximum(:id)

    maximum_id_in_database = maximum_id_in_table if maximum_id_in_table > maximum_id_in_database

  end

  maximum_id = maximum_id_in_database if maximum_id_in_database > maximum_id

end

puts "maximum id across all tables in all databases is #{maximum_id}"