#174 完了

backend/db/migrate/20251210123200_add_unique_index_to_tag_implications.rb

@@ -0,0 +1,7 @@
+class AddUniqueIndexToTagImplications < ActiveRecord::Migration[8.0]
+  def change
+    add_index :tag_implications, [:tag_id, :parent_tag_id],
+              unique: true,
+              name: 'index_tag_implications_on_tag_id_and_parent_tag_id'
+  end
+end