diff options
| -rw-r--r-- | activerecord/lib/active_record/associations/preloader/through_association.rb | 9 | ||||
| -rw-r--r-- | activerecord/test/cases/associations/eager_test.rb | 6 |
2 files changed, 13 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb index 24aa47bb51..6c83058202 100644 --- a/activerecord/lib/active_record/associations/preloader/through_association.rb +++ b/activerecord/lib/active_record/associations/preloader/through_association.rb @@ -18,7 +18,8 @@ module ActiveRecord through_records = owners.map do |owner| association = owner.association through_reflection.name - [owner, Array(association.reader)] + center = target_records_from_association(association) + [owner, Array(center)] end reset_association owners, through_reflection.name @@ -49,7 +50,7 @@ module ActiveRecord rhs_records = middles.flat_map { |r| association = r.association source_reflection.name - association.reader + target_records_from_association(association) }.compact rhs_records.sort_by { |rhs| record_offset[rhs] } @@ -91,6 +92,10 @@ module ActiveRecord scope end + + def target_records_from_association(association) + association.loaded? ? association.target : association.reader + end end end end diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb index 0c09713971..874d53c51f 100644 --- a/activerecord/test/cases/associations/eager_test.rb +++ b/activerecord/test/cases/associations/eager_test.rb @@ -1402,4 +1402,10 @@ class EagerAssociationTest < ActiveRecord::TestCase post = Post.eager_load(:tags).where('tags.name = ?', 'General').first assert_equal posts(:welcome), post end + + # CollectionProxy#reader is expensive, so the preloader avoids calling it. + test "preloading has_many_through association avoids calling association.reader" do + ActiveRecord::Associations::HasManyAssociation.any_instance.expects(:reader).never + Author.preload(:readonly_comments).first! + end end |