[Note: Had initially posted to SOLR-9506, but now moved here]
While working on
SOLR-5944, I realized that the current per segment caching logic works fine for deleted documents (due to comparison of numDocs in a segment for the criterion of cache hit/miss). However, if a segment has docValues updates, the same logic is insufficient. It is my understanding that changing the key for caching from reader().getCoreCacheKey() to reader().getCombinedCoreAndDeletesKey() would work here, since the docValues updates are internally handled using deletion queue and hence the "combined" core and deletes key would work here. Attaching a patch for the same.