Qualify column names in calculation

Column names inserted via `group` have to be qualified with table name.

activerecord/CHANGELOG.md

+*   Qualify column name inserted by `group` in calculation
+
+    Giving `group` an unqualified column name now works, even if the relation
+    has `JOIN` with another table which also has a column of the name.
+
+    *Soutaro Matsumoto*
+
 *   Don't cache prepared statements containing an IN clause or a SQL literal, as
     these queries will change often and are unlikely to have a cache hit.
 

activerecord/lib/active_record/relation/calculations.rb

@@ -297,7 +297,7 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
       ]
       select_values += select_values unless having_clause.empty?
 
-      select_values.concat group_fields.zip(group_aliases).map { |field,aliaz|
+      select_values.concat arel_columns(group_fields).zip(group_aliases).map { |field,aliaz|
         if field.respond_to?(:as)
           field.as(aliaz)
         else

activerecord/test/cases/calculations_test.rb

@@ -102,6 +102,25 @@ def test_should_group_by_summed_field
     assert_equal 60,   c[2]
   end
 
+  def test_should_generate_valid_sql_with_joins_and_group
+    assert_nothing_raised ActiveRecord::StatementInvalid do
+      AuditLog.joins(:developer).group(:id).count
+    end
+  end
+
+  def test_should_calculate_against_given_relation
+    developer = Developer.create!(name: "developer")
+    developer.audit_logs.create!(message: "first log")
+    developer.audit_logs.create!(message: "second log")
+
+    c = developer.audit_logs.joins(:developer).group(:id).count
+
+    assert_equal developer.audit_logs.count, c.size
+    developer.audit_logs.each do |log|
+      assert_equal 1, c[log.id]
+    end
+  end
+
   def test_should_order_by_grouped_field
     c = Account.group(:firm_id).order("firm_id").sum(:credit_limit)
     assert_equal [1, 2, 6, 9], c.keys.compact