Add unique indexes for Collection(Item) URIs (#38409)

db/migrate/20260325151755_add_unique_indexes_to_collections_and_items.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexesToCollectionsAndItems < ActiveRecord::Migration[8.1]
+  disable_ddl_transaction!
+
+  def change
+    add_index :collections, :uri, unique: true, where: 'uri IS NOT NULL', algorithm: :concurrently
+    add_index :collection_items, :uri, unique: true, where: 'uri IS NOT NULL', algorithm: :concurrently
+  end
+end