Extract `Relation#update_counters` for internal use

The target object for counter cache is not always determined by the
primary key value on the model. I'd like to extract `update_couters`
onto the `Relation` for the internal use.

4 files changed, 27 insertions, 34 deletions

diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index 08f450278d..3d4ad1dd5b 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -67,7 +67,7 @@ module ActiveRecord
             if target && !stale_target?
               target.increment!(reflection.counter_cache_column, by, touch: reflection.options[:touch])
             else
-              klass.update_counters(target_id, reflection.counter_cache_column => by, touch: reflection.options[:touch])
+              counter_cache_target.update_counters(reflection.counter_cache_column => by, touch: reflection.options[:touch])
             end
           end
         end
@@ -112,12 +112,9 @@ module ActiveRecord
           inverse && inverse.has_one?
         end
 
-        def target_id
-          if options[:primary_key]
-            owner.send(reflection.name).try(:id)
-          else
-            owner._read_attribute(reflection.foreign_key)
-          end
+        def counter_cache_target
+          primary_key = reflection.association_primary_key(klass)
+          klass.unscoped.where!(primary_key => owner._read_attribute(reflection.foreign_key))
         end
 
         def stale_state
diff --git a/activerecord/lib/active_record/associations/builder/belongs_to.rb b/activerecord/lib/active_record/associations/builder/belongs_to.rb
index 4b6cb76081..b5fb0092d7 100644
--- a/activerecord/lib/active_record/associations/builder/belongs_to.rb
+++ b/activerecord/lib/active_record/associations/builder/belongs_to.rb
@@ -48,14 +48,12 @@ module ActiveRecord::Associations::Builder # :nodoc:
             foreign_key_was = attribute_before_last_save foreign_key
             foreign_key     = attribute_in_database foreign_key
 
-            if foreign_key && model.respond_to?(:increment_counter)
-              foreign_key = counter_cache_target(reflection, model, foreign_key)
-              model.increment_counter(cache_column, foreign_key)
+            if foreign_key && model < ActiveRecord::Base
+              counter_cache_target(reflection, model, foreign_key).update_counters(cache_column => 1)
             end
 
-            if foreign_key_was && model_was.respond_to?(:decrement_counter)
-              foreign_key_was = counter_cache_target(reflection, model_was, foreign_key_was)
-              model_was.decrement_counter(cache_column, foreign_key_was)
+            if foreign_key_was && model_was < ActiveRecord::Base
+              counter_cache_target(reflection, model_was, foreign_key_was).update_counters(cache_column => -1)
             end
           end
         end
diff --git a/activerecord/lib/active_record/counter_cache.rb b/activerecord/lib/active_record/counter_cache.rb
index 0d8748d7e6..c7f0077a76 100644
--- a/activerecord/lib/active_record/counter_cache.rb
+++ b/activerecord/lib/active_record/counter_cache.rb
@@ -102,27 +102,7 @@ module ActiveRecord
       #   #    `updated_at` = '2016-10-13T09:59:23-05:00'
       #   #  WHERE id IN (10, 15)
       def update_counters(id, counters)
-        touch = counters.delete(:touch)
-
-        updates = counters.map do |counter_name, value|
-          operator = value < 0 ? "-" : "+"
-          quoted_column = connection.quote_column_name(counter_name)
-          "#{quoted_column} = COALESCE(#{quoted_column}, 0) #{operator} #{value.abs}"
-        end
-
-        if touch
-          names = touch if touch != true
-          touch_updates = touch_attributes_with_time(*names)
-          updates << sanitize_sql_for_assignment(touch_updates) unless touch_updates.empty?
-        end
-
-        if id.is_a?(Relation) && self == id.klass
-          relation = id
-        else
-          relation = unscoped.where!(primary_key => id)
-        end
-
-        relation.update_all updates.join(", ")
+        unscoped.where!(primary_key => id).update_counters(counters)
       end
 
       # Increment a numeric field by one, via a direct SQL update.
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index e7224658c4..e1cd5cbf29 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -369,6 +369,24 @@ module ActiveRecord
       @klass.connection.update stmt, "#{@klass} Update All"
     end
 
+    def update_counters(counters) # :nodoc:
+      touch = counters.delete(:touch)
+
+      updates = counters.map do |counter_name, value|
+        operator = value < 0 ? "-" : "+"
+        quoted_column = connection.quote_column_name(counter_name)
+        "#{quoted_column} = COALESCE(#{quoted_column}, 0) #{operator} #{value.abs}"
+      end
+
+      if touch
+        names = touch if touch != true
+        touch_updates = klass.touch_attributes_with_time(*names)
+        updates << klass.sanitize_sql_for_assignment(touch_updates) unless touch_updates.empty?
+      end
+
+      update_all updates.join(", ")
+    end
+
     # Touches all records in the current relation without instantiating records first with the updated_at/on attributes
     # set to the current time or the time specified.
     # This method can be passed attribute names and an optional time argument.