remove state from the preloader

activerecord/lib/active_record/associations/preloader.rb

@@ -46,8 +46,6 @@ class Preloader #:nodoc:
         autoload :BelongsTo,           'active_record/associations/preloader/belongs_to'
       end
 
-      attr_reader :records, :associations, :preload_scope, :model
-
       # Eager loads the named associations for the given Active Record record(s).
       #
       # In this description, 'association name' shall refer to the name passed
@@ -82,28 +80,20 @@ class Preloader #:nodoc:
       #   [ :books, :author ]
       #   { author: :avatar }
       #   [ :books, { author: :avatar } ]
-      def initialize(records, associations, preload_scope = nil)
-        @records       = Array.wrap(records).compact.uniq
-        @associations  = Array.wrap(associations)
-        @preload_scope = preload_scope || NULL_RELATION
-        @preloaders    = nil
-      end
 
       NULL_RELATION = Struct.new(:values).new({})
 
-      def run
-        preloaders.each(&:run)
-      end
-
-      def preloaders
-        return @preloaders if @preloaders
+      def preload(records, associations, preload_scope = nil)
+        records       = Array.wrap(records).compact.uniq
+        associations  = Array.wrap(associations)
+        preload_scope = preload_scope || NULL_RELATION
 
         if records.empty?
-          @preloaders = []
+          []
         else
-          @preloaders = associations.flat_map { |association|
+          associations.flat_map { |association|
             preloaders_on association, records, preload_scope
-          }
+          }.each(&:run)
         end
       end
 

activerecord/lib/active_record/associations/preloader/through_association.rb

@@ -16,10 +16,10 @@ def associated_records_by_owner
 
           return @associated_records_by_owner if @associated_records_by_owner
 
-          left_loader = Preloader.new(owners,
+          left_loader = Preloader.new
+          left_loader.preload(owners,
                               through_reflection.name,
                               through_scope)
-          left_loader.run
 
           should_reset = (through_scope != through_reflection.klass.unscoped) ||
              (reflection.options[:source_type] && through_reflection.collection?)
@@ -37,13 +37,12 @@ def associated_records_by_owner
 
           middle_records = through_records.map { |(_,rec,_)| rec }.flatten
 
-          preloader = Preloader.new(middle_records,
+          preloader = Preloader.new
+          preloaders = preloader.preload(middle_records,
                             source_reflection.name,
                             reflection_scope)
 
-          preloader.run
-
-          middle_to_pl = preloader.preloaders.each_with_object({}) do |pl,h|
+          middle_to_pl = preloaders.each_with_object({}) do |pl,h|
             pl.owners.each { |middle|
               h[middle] = pl
             }

activerecord/lib/active_record/relation.rb

@@ -600,7 +600,8 @@ def exec_queries
       preload = preload_values
       preload +=  includes_values unless eager_loading?
       preload.each do |associations|
-        ActiveRecord::Associations::Preloader.new(@records, associations).run
+        pl = ActiveRecord::Associations::Preloader.new
+        pl.preload @records, associations
       end
 
       @records.each { |record| record.readonly! } if readonly_value