Merge pull request #1 from mdluo/pr/18316

Fix n+1 query problem when eager loading nil associations (fixes #18312)

1 files changed, 8 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 371635d20a..7d8b933992 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -77,9 +77,17 @@ class EagerAssociationTest < ActiveRecord::TestCase
 
   def test_has_many_through_with_order
     authors = Author.includes(:favorite_authors).to_a
+    assert authors.count > 0
     assert_no_queries { authors.map(&:favorite_authors) }
   end
 
+  def test_eager_loaded_has_one_association_with_references_does_not_run_additional_queries
+    Post.update_all(author_id: nil)
+    authors = Author.includes(:post).references(:post).to_a
+    assert authors.count > 0
+    assert_no_queries { authors.map(&:post) }
+  end
+
   def test_with_two_tables_in_from_without_getting_double_quoted
     posts = Post.select("posts.*").from("authors, posts").eager_load(:comments).where("posts.author_id = authors.id").order("posts.id").to_a
     assert_equal 2, posts.first.comments.size