You can add the "id" attribue to your index's attributesForFaceting in your Algolia Shopify app by following these steps:
- Navigate to the Algolia Shopify app
- Go to the Search options tab > InstantSearch 'Customize' and scroll down to Facets configuration
- Add the "Id" attribute. Once the "Id" attribute appears in the Inactive list, click the + button to activate it
- Hover your mouse over the "Id" facet, and click 'Edit' to modify the type to "hidden." This way the "Id" attribute will be used only for filtering and will not be displayed as a facet filter on your theme's frontend.
- Click the "Save" button.