Referencing a table via the ON condition in a join should force that table to be eager-loaded via a JOIN rather than via subsequent queries.

1 files changed, 15 insertions, 0 deletions

diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 54537f11a8..ac586e2a63 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -850,4 +850,19 @@ class RelationTest < ActiveRecord::TestCase
   def test_primary_key
     assert_equal "id", Post.scoped.primary_key
   end
+
+  def test_eager_loading_with_conditions_on_joins
+    scope = Post.includes(:comments)
+
+    # This references the comments table, and so it should cause the comments to be eager
+    # loaded via a JOIN, rather than by subsequent queries.
+    scope = scope.joins(
+      Post.arel_table.create_join(
+        Post.arel_table,
+        Post.arel_table.create_on(Comment.arel_table[:id].eq(3))
+      )
+    )
+
+    assert scope.eager_loading?
+  end
 end