speed up finding existing nodes

The node must be a child of the parent passed in, so only search
children of the parent node

1 files changed, 1 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index fe0066bbe1..199d28426b 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -203,9 +203,7 @@ module ActiveRecord
       end
 
       def find_join_association(reflection, parent)
-        join_associations.detect { |j|
-          j.reflection == reflection && node_cmp(j.parent, parent)
-        }
+        parent.children.find { |j| j.reflection == reflection }
       end
 
       def remove_uniq_by_reflection(reflection, records)