message: allow set doc store cache size on IndexReaderBuilder
diff: @@ -124,6 +124,15 @@ impl IndexReaderBuilder {
  self
  }
  + /// Sets the cache size of the doc store readers.
  + ///
  + /// The doc store readers cache by default DOCSTORE_CACHE_CAPACITY(100) decompressed blocks.
  + #[must_use]
  + pub fn doc_store_cache_size(mut self, doc_store_cache_size: usize) -> IndexReaderBuilder {
  + self.doc_store_cache_size = doc_store_cache_size;
  + self
  + }
  +
  /// Sets the number of [Searcher] to pool.
  ///
  /// See [IndexReader::searcher()].
  