Remove delegating to arel in a relation

The delegation was needed since passing `relation` with
`relation.bound_attributes`. It should use `relation.arel` in that case.

activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb

@@ -123,6 +123,7 @@ module ActiveRecord
         # If arel is locked this is a SELECT ... FOR UPDATE or somesuch. Such
         # queries should not be cached.
         def locked?(arel)
+          arel = arel.arel if arel.is_a?(Relation)
           arel.respond_to?(:locked) && arel.locked
         end
 

activerecord/lib/active_record/relation/calculations.rb

@@ -311,7 +311,7 @@ module ActiveRecord
         relation.group_values  = group_fields
         relation.select_values = select_values
 
-        calculated_data = @klass.connection.select_all(relation, nil, relation.bound_attributes)
+        calculated_data = @klass.connection.select_all(relation.arel, nil, relation.bound_attributes)
 
         if association
           key_ids     = calculated_data.collect { |row| row[group_aliases.first] }

activerecord/lib/active_record/relation/delegation.rb

@@ -44,8 +44,6 @@ module ActiveRecord
     delegate :table_name, :quoted_table_name, :primary_key, :quoted_primary_key,
              :connection, :columns_hash, to: :klass
 
-    delegate :ast, :locked, to: :arel
-
     module ClassSpecificRelation # :nodoc:
       extend ActiveSupport::Concern
 

activerecord/lib/active_record/relation/finder_methods.rb

@@ -316,7 +316,7 @@ module ActiveRecord
 
       relation = construct_relation_for_exists(relation, conditions)
 
-      connection.select_value(relation, "#{name} Exists", relation.bound_attributes) ? true : false
+      connection.select_value(relation.arel, "#{name} Exists", relation.bound_attributes) ? true : false
     rescue ::RangeError
       false
     end
@@ -377,8 +377,7 @@ module ActiveRecord
           if ActiveRecord::NullRelation === relation
             []
           else
-            arel = relation.arel
-            rows = connection.select_all(arel, "SQL", relation.bound_attributes)
+            rows = connection.select_all(relation.arel, "SQL", relation.bound_attributes)
             join_dependency.instantiate(rows, aliases)
           end
         end
@@ -425,9 +424,8 @@ module ActiveRecord
           "#{quoted_table_name}.#{quoted_primary_key}", relation.order_values)
 
         relation = relation.except(:select).select(values).distinct!
-        arel = relation.arel
 
-        id_rows = @klass.connection.select_all(arel, "SQL", relation.bound_attributes)
+        id_rows = @klass.connection.select_all(relation.arel, "SQL", relation.bound_attributes)
         id_rows.map { |row| row[primary_key] }
       end
 

activerecord/test/cases/relations_test.rb

@@ -2002,7 +2002,7 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_locked_should_not_build_arel
-    posts = Post.lock
+    posts = Post.locked
     assert posts.locked?
     assert_nothing_raised { posts.lock!(false) }
   end

activerecord/test/models/post.rb

@@ -22,6 +22,7 @@ class Post < ActiveRecord::Base
   scope :ranked_by_comments,      -> { order("comments_count DESC") }
 
   scope :limit_by, lambda { |l| limit(l) }
+  scope :locked, -> { lock }
 
   belongs_to :author
   belongs_to :readonly_author, -> { readonly }, class_name: "Author", foreign_key: :author_id