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@@ -1,5 +1,7 @@
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 *Edge*
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+* Add :from option to calculations.  #397 [Ben Munat]
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+
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 * Add :validate option to associations to enable/disable the automatic validation of associated models. Resolves #301. [Jan De Poorter]
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 * PostgreSQL: use 'INSERT ... RETURNING id' for 8.2 and later.  [Jeremy Kemper]

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@@ -1,6 +1,6 @@
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 module ActiveRecord
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   module Calculations #:nodoc:
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-    CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include]
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+    CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include, :from]
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     def self.included(base)
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       base.extend(ClassMethods)
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     end
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@@ -27,6 +27,8 @@ module ActiveRecord
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       # * <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
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       #   include the joined columns.
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       # * <tt>:distinct</tt>: Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ...
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+      # * <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
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+      #   of a database view).
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       #
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       # Examples for counting all:
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       #   Person.count         # returns the total count of all people
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@@ -178,8 +180,12 @@ module ActiveRecord
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           sql = "SELECT COUNT(*) AS #{aggregate_alias}" if use_workaround
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           sql << ", #{options[:group_field]} AS #{options[:group_alias]}" if options[:group]
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-          sql << " FROM (SELECT #{distinct}#{column_name}" if use_workaround
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-          sql << " FROM #{connection.quote_table_name(table_name)} "
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+          if options[:from]
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+            sql << " FROM #{options[:from]} "
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+          else
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+            sql << " FROM (SELECT #{distinct}#{column_name}" if use_workaround
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+            sql << " FROM #{connection.quote_table_name(table_name)} "
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+          end
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           if merged_includes.any?
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             join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_includes, options[:joins])
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             sql << join_dependency.join_associations.collect{|join| join.association_join }.join

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@@ -1,6 +1,7 @@
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 require "cases/helper"
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 require 'models/company'
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 require 'models/topic'
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+require 'models/edge'
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 Company.has_many :accounts
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@@ -274,4 +275,49 @@ class CalculationsTest < ActiveRecord::TestCase
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   def test_should_sum_expression
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     assert_equal 636, Account.sum("2 * credit_limit")
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   end
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+
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+  def test_count_with_from_option
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+    assert_equal Company.count(:all), Company.count(:all, :from => 'companies')
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+    assert_equal Account.count(:all, :conditions => "credit_limit = 50"),
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+        Account.count(:all, :from => 'accounts', :conditions => "credit_limit = 50")
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+    assert_equal Company.count(:type, :conditions => {:type => "Firm"}),
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+        Company.count(:type, :conditions => {:type => "Firm"}, :from => 'companies')
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+  end
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+
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+  def test_sum_with_from_option
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+    assert_equal Account.sum(:credit_limit), Account.sum(:credit_limit, :from => 'accounts')
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+    assert_equal Account.sum(:credit_limit, :conditions => "credit_limit > 50"),
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+        Account.sum(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
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+  end
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+
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+  def test_average_with_from_option
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+    assert_equal Account.average(:credit_limit), Account.average(:credit_limit, :from => 'accounts')
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+    assert_equal Account.average(:credit_limit, :conditions => "credit_limit > 50"),
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+        Account.average(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
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+  end
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+
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+  def test_minimum_with_from_option
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+    assert_equal Account.minimum(:credit_limit), Account.minimum(:credit_limit, :from => 'accounts')
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+    assert_equal Account.minimum(:credit_limit, :conditions => "credit_limit > 50"),
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+        Account.minimum(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
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+  end
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+
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+  def test_maximum_with_from_option
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+    assert_equal Account.maximum(:credit_limit), Account.maximum(:credit_limit, :from => 'accounts')
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+    assert_equal Account.maximum(:credit_limit, :conditions => "credit_limit > 50"),
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+        Account.maximum(:credit_limit, :from => 'accounts', :conditions => "credit_limit > 50")
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+  end
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+
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+  def test_from_option_with_specified_index
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+    if Edge.connection.adapter_name == 'MySQL'
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+      assert_equal Edge.count(:all), Edge.count(:all, :from => 'edges USE INDEX(unique_edge_index)')
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+      assert_equal Edge.count(:all, :conditions => 'sink_id < 5'),
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+          Edge.count(:all, :from => 'edges USE INDEX(unique_edge_index)', :conditions => 'sink_id < 5')
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+    end
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+  end
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+
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+  def test_from_option_with_table_different_than_class
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+    assert_equal Account.count(:all), Company.count(:all, :from => 'accounts')
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+  end
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+
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 end