Add :from option to calculations. [#397 state:resolved]

3 files changed, 57 insertions, 3 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index b726962872..a1d82fb45d 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *Edge*
 
+* Add :from option to calculations.  #397 [Ben Munat]
+
 * Add :validate option to associations to enable/disable the automatic validation of associated models. Resolves #301. [Jan De Poorter]
 
 * PostgreSQL: use 'INSERT ... RETURNING id' for 8.2 and later.  [Jeremy Kemper]
diff --git a/activerecord/lib/active_record/calculations.rb b/activerecord/lib/active_record/calculations.rb
index caa8c539d5..2ca1a0aaa3 100644
--- a/activerecord/lib/active_record/calculations.rb
+++ b/activerecord/lib/active_record/calculations.rb
@@ -1,6 +1,6 @@
 module ActiveRecord
   module Calculations #:nodoc:
-    CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include]
+    CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include, :from]
     def self.included(base)
       base.extend(ClassMethods)
     end
@@ -27,6 +27,8 @@ module ActiveRecord
       # * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you, for example, want to do a join but not
       #   include the joined columns.
       # * <tt>:distinct</tt>: Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ...
+      # * <tt>:from</tt> - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name
+      #   of a database view).
       #
       # Examples for counting all:
       #   Person.count         # returns the total count of all people
@@ -178,8 +180,12 @@ module ActiveRecord
           sql = "SELECT COUNT(*) AS #{aggregate_alias}" if use_workaround
 
           sql << ", #{options[:group_field]} AS #{options[:group_alias]}" if options[:group]
-          sql << " FROM (SELECT #{distinct}#{column_name}" if use_workaround
-          sql << " FROM #{connection.quote_table_name(table_name)} "
+          if options[:from]
+            sql << " FROM #{options[:from]} "
+          else
+            sql << " FROM (SELECT #{distinct}#{column_name}" if use_workaround
+            sql << " FROM #{connection.quote_table_name(table_name)} "
+          end
           if merged_includes.any?
             join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_includes, options[:joins])
             sql << join_dependency.join_associations.collect{|join| join.association_join }.join
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index aefb13ea9a..754fd58f35 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -1,6 +1,7 @@
 require "cases/helper"
 require 'models/company'
 require 'models/topic'
+require 'models/edge'
 
 Company.has_many :accounts
 
@@ -274,4 +275,49 @@ class CalculationsTest < ActiveRecord::TestCase
   def test_should_sum_expression
     assert_equal 636, Account.sum("2 * credit_limit")
   end
+
+  def test_count_with_from_option
+    assert_equal Company.count(:all), Company.count(:all, :from => 'companies')
+    assert_equal Account.count(:all, :conditions => "credit_limit = 50"),
+        Account.count(:all, :from => 'accounts', :conditions => "credit_limit = 50")
+    assert_equal Company.count(:type, :conditions => {:type => "Firm"}),
+        Company.count(:type, :conditions => {:type => "Firm"}, :from => 'companies')
+  end
+
+  def test_sum_with_from_option
+    assert_equal Account.sum(:credit_limit), Account.sum(:credit_limit, :from => 'accounts')
+    assert_equal Account.sum(:credit_limit, :conditions => "credit_limit > 50"),
+        Account.sum(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
+  end
+
+  def test_average_with_from_option
+    assert_equal Account.average(:credit_limit), Account.average(:credit_limit, :from => 'accounts')
+    assert_equal Account.average(:credit_limit, :conditions => "credit_limit > 50"),
+        Account.average(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
+  end
+
+  def test_minimum_with_from_option
+    assert_equal Account.minimum(:credit_limit), Account.minimum(:credit_limit, :from => 'accounts')
+    assert_equal Account.minimum(:credit_limit, :conditions => "credit_limit > 50"),
+        Account.minimum(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
+  end
+
+  def test_maximum_with_from_option
+    assert_equal Account.maximum(:credit_limit), Account.maximum(:credit_limit, :from => 'accounts')
+    assert_equal Account.maximum(:credit_limit, :conditions => "credit_limit > 50"),
+        Account.maximum(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
+  end
+
+  def test_from_option_with_specified_index
+    if Edge.connection.adapter_name == 'MySQL'
+      assert_equal Edge.count(:all), Edge.count(:all, :from => 'edges USE INDEX(unique_edge_index)')
+      assert_equal Edge.count(:all, :conditions => 'sink_id < 5'),
+          Edge.count(:all, :from => 'edges USE INDEX(unique_edge_index)', :conditions => 'sink_id < 5')
+    end
+  end
+
+  def test_from_option_with_table_different_than_class
+    assert_equal Account.count(:all), Company.count(:all, :from => 'accounts')
+  end
+
 end