Adding :from scoping to ActiveRecord calculations

Signed-off-by: NMichael Koziarski <michael@koziarski.com>
[#1229 state:committed]

activerecord/lib/active_record/calculations.rb

@@ -197,6 +197,8 @@ def construct_calculation_sql(operation, column_name, options) #:nodoc:
           sql << ", #{options[:group_field]} AS #{options[:group_alias]}" if options[:group]
           if options[:from]
             sql << " FROM #{options[:from]} "
+          elsif scope && scope[:from]
+            sql << " FROM #{scope[:from]} "
           else
             sql << " FROM (SELECT #{distinct}#{column_name}" if use_workaround
             sql << " FROM #{connection.quote_table_name(table_name)} "

activerecord/test/cases/calculations_test.rb

@@ -2,6 +2,8 @@
 require 'models/company'
 require 'models/topic'
 require 'models/edge'
+require 'models/club'
+require 'models/organization'
 
 Company.has_many :accounts
 
@@ -223,6 +225,10 @@ def test_should_sum_scoped_field
     assert_equal 15, companies(:rails_core).companies.sum(:id)
   end
 
+  def test_should_sum_scoped_field_with_from
+    assert_equal Club.count, Organization.clubs.count
+  end
+
   def test_should_sum_scoped_field_with_conditions
     assert_equal 8,  companies(:rails_core).companies.sum(:id, :conditions => 'id > 7')
   end

activerecord/test/models/organization.rb

 class Organization < ActiveRecord::Base
   has_many :member_details
   has_many :members, :through => :member_details
+
+  named_scope :clubs, { :from => 'clubs' }
 end
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