rake db:schema:dump_all

schema.rake

namespace :db do
  namespace :schema do
    # desc 'Dump all database schema'
    task :dump_all => [:environment, :load_config] do
      ActiveRecord::Base.configurations.keys.grep(/_development$/).map{|o|o.sub "_development", ""}.each do |name|
        begin
          filename = "#{Rails.root}/db/#{name}_schema.rb"
          File.open(filename, 'w:utf-8') do |file|
            ActiveRecord::Base.establish_connection("#{name}_#{Rails.env}")
            ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
          end
        rescue
        end
      end
    end
  end
end