Document how the :include option can be used in Calculations::calculate. ...

Document how the :include option can be used in Calculations::calculate.  Closes #7446 [adamwiggins, ultimoamore]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8306 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Document how the :include option can be used in Calculations::calculate.  Closes #7446 [adamwiggins, ultimoamore]
+
 * Fix typo in documentation for polymorphic associations w/STI. Closes #7461 [johnjosephbachir]
 
 * Reveal that the type option in migrations can be any supported column type for your database but also include caveat about agnosticism. Closes #7531 [adamwiggins, mikong]

activerecord/lib/active_record/calculations.rb

@@ -20,6 +20,7 @@ module ClassMethods
       #   If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table's columns.
       #   Pass :readonly => false to override.
       #   See adding joins for associations under Associations.
+      #
       # * <tt>:include</tt>: Named associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer
       #   to already defined associations. When using named associations, count returns the number of DISTINCT items for the model you're counting.
       #   See eager loading under Associations.
@@ -98,6 +99,7 @@ def sum(column_name, options = {})
       #
       # Options:
       # * <tt>:conditions</tt> - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro.
+      # * <tt>:include</tt>: Eager loading, see Associations for details.  Since calculations don't load anything, the purpose of this is to access fields on joined tables in your conditions, order, or group clauses.
       # * <tt>:joins</tt> - An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed).
       #   The records will be returned read-only since they will have attributes that do not correspond to the table's columns.
       # * <tt>:order</tt> - An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations).