Implement ActiveRecord#reset_counter_cache

[#1211 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *Edge*
 
+* Reset your Active Record counter caches with the reset_counter_cache class method.  #1211 [Mike Breen]
+
 * Remove support for SQLite 2. Please upgrade to SQLite 3+ or install the plugin from git://github.com/rails/sqlite2_adapter.git [Pratik Naik]
 
 * PostgreSQL: XML datatype support.  #1874 [Leonardo Borges]

activerecord/lib/active_record/base.rb

@@ -967,6 +967,24 @@ module ActiveRecord #:nodoc:
         connection.select_value(sql, "#{name} Count").to_i
       end
 
+      # Reset a counter cache for all records.
+      #
+      # ==== Parameters
+      #
+      # * +association_name+ - The name of of the association counter cache to reset
+      #
+      # ==== Examples
+      #   # For all Post records reset the comments_count
+      #   Post.reset_counter_cache(:comments)
+      def reset_counter_cache(association)
+        child_class = reflect_on_association(association).klass
+        counter_name = child_class.reflect_on_association(self.name.downcase.to_sym).counter_cache_column
+
+        find_each do |object|
+          connection.update("UPDATE #{quoted_table_name} SET #{connection.quote_column_name(counter_name)} = #{object.send(association).count} WHERE #{connection.quote_column_name(primary_key)} = #{quote_value(object.id)}", "#{name} UPDATE")
+        end
+      end
+
       # A generic "counter updater" implementation, intended primarily to be
       # used by increment_counter and decrement_counter, but which may also
       # be useful on its own. It simply does a direct SQL update for the record

activerecord/test/cases/base_test.rb

@@ -680,6 +680,16 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal -2, Topic.find(2).replies_count
   end
 
+  def test_reset_counter_cache
+    assert_equal 1, Topic.find(1).replies_count
+
+    Topic.increment_counter("replies_count", 1)
+    assert_equal 2, Topic.find(1).replies_count
+
+    Topic.reset_counter_cache(:replies)
+    assert_equal 1, Topic.find(1).replies_count
+  end
+
   def test_update_counter
     category = categories(:general)
     assert_nil category.categorizations_count