I am trying to figure out how WooCommerce decides which product attribute filters to bring. Because it does not only bring filterable attributes of the products in first page of an archive, but also brings attributes of other products on next pages to be used as filters.

I tested this by adding an attribute to one of the sample products that does not appear on the first page of the archive. And it works. WooCommerce somehow knows about the filterable product attributes of products that are not in the query result of an archive page.

Does anybody know how? How can we query product attributes of all of the products of an archive page (like product category or search result page) to be used for filters? I assume it does not query all of the products in an archive of lets say 200 products, because that would be extremely costly in terms of database usage.