From https://once.com/writebook

db/migrate/20240625084002_add_body_to_sections.rb

@@ -0,0 +1,9 @@
+class AddBodyToSections < ActiveRecord::Migration[8.0]
+  def change
+    change_table :sections do |t|
+      t.text :body
+    end
+
+    execute "update sections set body = l.title from leaves l where l.leafable_id = sections.id and l.leafable_type = 'Section'"
+  end
+end