Currently, the filter and id cache are only available on the node stats API (with the indices option), but not as part of the index stats API (because they are not kept on the shard level). Add them to the indices stats API (enabled using the filter_cache flag, and id_cache flag, or the respective URIs endpoints), and while at it, revise the node stats API to include the filter_cache and id_cache as top level elements in under indices response, and not under cache.