Add quick benchmark

activerecord/lib/active_record/relation.rb

@@ -838,7 +838,14 @@ def self.strict_loading_value
 
     def preload_associations(records) # :nodoc:
       preload = preload_values
-      preload += eager_loading? ? includes_values_non_referenced : includes_values
+      if ENV["SLIM_PATCH"].present?
+        preload += eager_loading? ? includes_values_non_referenced : includes_values
+      elsif ENV["SLIM_PATCH_CODE_ONLY"].present?
+        includes_values_non_referenced
+        preload += includes_values unless eager_loading?
+      else
+        preload += includes_values unless eager_loading?
+      end
       scope = strict_loading_value ? StrictLoadingScope : nil
       preload.each do |associations|
         ActiveRecord::Associations::Preloader.new(records: records, associations: associations, scope: scope).call

activerecord/lib/active_record/relation/finder_methods.rb

@@ -408,10 +408,21 @@ def construct_relation_for_exists(conditions)
       end
 
       def apply_join_dependency(eager_loading: group_values.empty?, full_eager_loading: false)
-        selected_includes_values = full_eager_loading ? includes_values : includes_values_referenced
-        join_dependency = construct_join_dependency(
-          eager_load_values | selected_includes_values, Arel::Nodes::OuterJoin
-        )
+        if ENV["SLIM_PATCH"].present?
+          selected_includes_values = full_eager_loading ? includes_values : includes_values_referenced
+          join_dependency = construct_join_dependency(
+            eager_load_values | selected_includes_values, Arel::Nodes::OuterJoin
+          )
+        elsif ENV["SLIM_PATCH_CODE_ONLY"].present?
+          selected_includes_values = full_eager_loading ? includes_values : includes_values_referenced
+          join_dependency = construct_join_dependency(
+            eager_load_values | includes_values, Arel::Nodes::OuterJoin
+          )
+        else
+          join_dependency = construct_join_dependency(
+            eager_load_values | includes_values, Arel::Nodes::OuterJoin
+          )
+        end
         relation = except(:includes, :eager_load, :preload).joins!(join_dependency)
 
         if eager_loading && has_limit_or_offset? && !(

activerecord/test/cases/associations/performance_test.rb

@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "cases/encryption/helper"
+require "models/author"
+require "models/book"
+require "models/citation"
+require "models/reader"
+require "models/post"
+require "models/reference"
+require "models/comment"
+require "models/rating"
+require "models/category"
+require "models/categorization"
+require "models/tag"
+require "models/tagging"
+require "models/person"
+require "models/club"
+require "models/developer"
+require "models/project"
+require "models/computer"
+require "models/company"
+require "models/contract"
+require "models/member"
+require "models/membership"
+require "models/sponsor"
+
+class AssociationsPerformanceTest < ActiveRecord::TestCase
+  include ActiveRecord::Encryption::PerformanceHelpers
+
+  fixtures :authors, :books, :citations, :readers, :posts, :references, :comments, :ratings,
+    :categories, :categorizations, :tags, :taggings, :people, :clubs, :members, :memberships,
+    :sponsors, :developers, :projects, :developers_projects, :computers, :companies, :accounts
+
+  DURATION = 10
+
+  def test_performance_tree_code_only
+    baseline = lambda do
+      ENV["SLIM_PATCH_CODE_ONLY"] = nil
+      ENV["SLIM_PATCH"] = nil
+      authors = Author.includes(
+        :books, { posts: :special_comments }, { categorizations: :category }
+      ).order("comments.body").where("posts.id = 4")
+      authors.to_a
+    end
+
+    assert_slower_by_at_most 1.05, baseline: baseline, duration: DURATION do
+      ENV["SLIM_PATCH_CODE_ONLY"] = "true"
+      ENV["SLIM_PATCH"] = nil
+      authors = Author.includes(
+        :books, { posts: :special_comments }, { categorizations: :category }
+      ).order("comments.body").where("posts.id = 4")
+      authors.to_a
+    end
+  end
+
+  def test_performance_objects_allocating
+    baseline = lambda do
+      ENV["SLIM_PATCH_CODE_ONLY"] = nil
+      ENV["SLIM_PATCH"] = nil
+      authors = Author.includes(
+        :books, { posts: :special_comments }, { categorizations: :category }
+      ).order("comments.body").where("posts.id = 4")
+      authors.to_a
+    end
+
+    assert_slower_by_at_most 1.2, baseline: baseline, duration: DURATION do
+      ENV["SLIM_PATCH_CODE_ONLY"] = nil
+      ENV["SLIM_PATCH"] = "true"
+      authors = Author.includes(
+        :books, { posts: :special_comments }, { categorizations: :category }
+      ).order("comments.body").where("posts.id = 4")
+      authors.to_a
+    end
+  end
+
+  def test_performance_sql_only
+    baseline = lambda do
+      ENV["SLIM_PATCH_CODE_ONLY"] = nil
+      ENV["SLIM_PATCH"] = nil
+      authors = Author.includes(
+        :books, { posts: :special_comments }, { categorizations: :category }
+      ).order("comments.body").where("posts.id = 4")
+      authors.to_sql
+    end
+
+    assert_slower_by_at_most 0.7, baseline: baseline, duration: DURATION do
+      ENV["SLIM_PATCH_CODE_ONLY"] = nil
+      ENV["SLIM_PATCH"] = "true"
+      authors = Author.includes(
+        :books, { posts: :special_comments }, { categorizations: :category }
+      ).order("comments.body").where("posts.id = 4")
+      authors.to_sql
+    end
+  end
+end