2 files changed, 9 insertions, 7 deletions
diff --git a/activerecord/lib/active_record/associations/builder/belongs_to.rb b/activerecord/lib/active_record/associations/builder/belongs_to.rb
index 1759a41d93..d78717704c 100644
--- a/activerecord/lib/active_record/associations/builder/belongs_to.rb
+++ b/activerecord/lib/active_record/associations/builder/belongs_to.rb
@@ -34,7 +34,10 @@ module ActiveRecord::Associations::Builder
         method_name = "belongs_to_counter_cache_before_destroy_for_#{name}"
         mixin.redefine_method(method_name) do
           record = send(name)
-          record.class.decrement_counter(cache_column, record.id) unless record.nil?
+
+          if record && !self.destroyed?
+            record.class.decrement_counter(cache_column, record.id)
+          end
         end
         model.before_destroy(method_name)
 
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 1f9dbdc3d4..d4765a6782 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -179,14 +179,13 @@ module ActiveRecord
     def pluck(column_name)
       if column_name.is_a?(Symbol) && column_names.include?(column_name.to_s)
         column_name = "#{connection.quote_table_name(table_name)}.#{connection.quote_column_name(column_name)}"
-      else
-        column_name = column_name.to_s
       end
 
-      relation = clone
-      relation.select_values = [column_name]
-      klass.connection.select_all(relation.arel).map! do |attributes|
-        klass.type_cast_attribute(attributes.keys.first, klass.initialize_attributes(attributes))
+      result = klass.connection.exec_query(select(column_name).to_sql)
+      last_column = result.columns.last
+
+      klass.connection.select_all(select(column_name).arel).map! do |attributes|
+        klass.type_cast_attribute(last_column, klass.initialize_attributes(attributes))
       end
     end