01 May 08 Dirty models and partial SQL updates for Rails 2.0.2

module ActiveRecord
 
  class Base
 
	  # Updates the associated record with values matching those of the instance attributes.
 
	  # Returns the number of affected rows.
 
	  def update(attribute_names = @attributes.keys)
 
		quoted_attributes = attributes_with_quotes(false, false, attribute_names)
 
		return 0 if quoted_attributes.empty?
 
		connection.update(
 
		  "UPDATE #{self.class.quoted_table_name} " +
 
		  "SET #{quoted_comma_pair_list(connection, quoted_attributes)} " +
 
		  "WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quote_value(id)}",
 
		  "#{self.class.name} Update"
 
		)
 
	  end
 
      # Returns a copy of the attributes hash where all the values have been safely quoted for use in
 
     # an SQL statement.
 
     def attributes_with_quotes(include_primary_key = true, include_readonly_attributes = true, attribute_names = @attributes.keys)
 
       quoted = {}
 
       connection = self.class.connection
 
       attribute_names.each do |name|
 
         if column = column_for_attribute(name)
 
           quoted[name] = connection.quote(read_attribute(name), column) unless !include_primary_key && column.primary
 
         end
 
       end
 
       include_readonly_attributes ? quoted : remove_readonly_attributes(quoted)
 
     end
 
  end
 
  # Track unsaved attribute changes.
 
  #
 
  # A newly instantiated object is unchanged:
 
  #   person = Person.find_by_name('uncle bob')
 
  #   person.changed?       # => false
 
  #
 
  # Change the name:
 
  #   person.name = 'Bob'
 
  #   person.changed?       # => true
 
  #   person.name_changed?  # => true
 
  #   person.name_was       # => 'uncle bob'
 
  #   person.name_change    # => ['uncle bob', 'Bob']
 
  #   person.name = 'Bill'
 
  #   person.name_change    # => ['uncle bob', 'Bill']
 
  #
 
  # Save the changes:
 
  #   person.save
 
  #   person.changed?       # => false
 
  #   person.name_changed?  # => false
 
  #
 
  # Assigning the same value leaves the attribute unchanged:
 
  #   person.name = 'Bill'
 
  #   person.name_changed?  # => false
 
  #   person.name_change    # => nil
 
  #
 
  # Which attributes have changed?
 
  #   person.name = 'bob'
 
  #   person.changed        # => ['name']
 
  #   person.changes        # => { 'name' => ['Bill', 'bob'] }
 
  #
 
  # Before modifying an attribute in-place:
 
  #   person.name_will_change!
 
  #   person.name << 'by'
 
  #   person.name_change    # => ['uncle bob', 'uncle bobby']
 
  module Dirty
 
    def self.included(base)
 
      base.attribute_method_suffix '_changed?', '_change', '_will_change!', '_was'
 
      base.alias_method_chain :write_attribute, :dirty
 
      base.alias_method_chain :save,            :dirty
 
      base.alias_method_chain :save!,           :dirty
 
      base.alias_method_chain :update,          :dirty
 
 
 
      base.superclass_delegating_accessor :partial_updates
 
      base.partial_updates = true
 
    end
 
 
 
    # Do any attributes have unsaved changes?
 
    #   person.changed? # => false
 
    #   person.name = 'bob'
 
    #   person.changed? # => true
 
    def changed?
 
      !changed_attributes.empty?
 
    end
 
 
 
    # List of attributes with unsaved changes.
 
    #   person.changed # => []
 
    #   person.name = 'bob'
 
    #   person.changed # => ['name']
 
    def changed
 
      changed_attributes.keys
 
    end
 
 
 
    # Map of changed attrs => [original value, new value]
 
    #   person.changes # => {}
 
    #   person.name = 'bob'
 
    #   person.changes # => { 'name' => ['bill', 'bob'] }
 
    def changes
 
      changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h }
 
    end
 
 
 
 
 
    # Clear changed attributes after they are saved.
 
    def save_with_dirty(*args) #:nodoc:
 
      save_without_dirty(*args)
 
    ensure
 
      changed_attributes.clear
 
    end
 
 
 
    # Clear changed attributes after they are saved.
 
    def save_with_dirty!(*args) #:nodoc:
 
      save_without_dirty!(*args)
 
    ensure
 
      changed_attributes.clear
 
    end
 
 
 
    def self.partial_updates?
 
      @partial_updates
 
    end
 
 
 
    private
 
      # Map of change attr => original value.
 
      def changed_attributes
 
        @changed_attributes ||= {}
 
      end
 
 
 
      # Handle *_changed? for method_missing.
 
      def attribute_changed?(attr)
 
        changed_attributes.include?(attr)
 
      end
 
 
 
      # Handle *_change for method_missing.
 
      def attribute_change(attr)
 
        [changed_attributes[attr], __send__(attr)] if attribute_changed?(attr)
 
      end
 
 
 
      # Handle *_was for method_missing.
 
      def attribute_was(attr)
 
        attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
 
      end
 
 
 
      # Handle *_will_change! for method_missing.
 
      def attribute_will_change!(attr)
 
        changed_attributes[attr] = clone_attribute_value(:read_attribute, attr)
 
      end
 
 
 
      # Wrap write_attribute to remember original attribute value.
 
      def write_attribute_with_dirty(attr, value)
 
        attr = attr.to_s
 
 
 
        # The attribute already has an unsaved change.
 
        unless changed_attributes.include?(attr)
 
          old = clone_attribute_value(:read_attribute, attr)
 
 
 
          # Remember the original value if it's different.
 
          typecasted = if column = column_for_attribute(attr)
 
                         column.type_cast(value)
 
                       else
 
                         value
 
                       end
 
          changed_attributes[attr] = old unless old == typecasted
 
        end
 
 
 
        # Carry on.
 
        write_attribute_without_dirty(attr, value)
 
      end
 
 
 
      def update_with_dirty
 
        update_without_dirty(changed)
 
      end
 
  end
 
end
 
 
 
ActiveRecord::Base.send :include, ActiveRecord::Dirty
 
#ActiveRecord::Base.partial_updates = true -- Now there is no way to disable this ugly partial updates hack