class Sequel::Dataset::DatasetModule

# SELECT id, name FROM table WHERE active ORDER BY id<br>DB.active.with_id_and_name.by_id
end
where :active, :active
select :with_id_and_name, :id, :name
order :by_id, :id
DB.extend_datasets do
For example:
named methods on the dataset instances which do specific actions.
It adds some helper methods inside the module that can define
and Dataset#with_extend to add dataset methods to classes.
This Module subclass is used by Database#extend_datasets

def self.def_dataset_caching_method(mod, meth)

Define a method in the module 
def self.def_dataset_caching_method(mod, meth)
  mod.send(:define_method, meth) do |name, *args, &block|
    if block
      define_method(name){public_send(meth, *args, &block)}
    else
      key = :"_#{meth}_#{name}_ds"
      define_method(name) do
        cached_dataset(key){public_send(meth, *args)}
      end
    end
  end
end