private long countMemStoreScanner(StoreScanner scanner) {
    if (scanner.currentScanners == null) {
      return 0;
    }
    return scanner.currentScanners.stream().filter(s -> !s.isFileScanner()).count();
  }
Test for HBASE-3492 - Test split on empty colfam (no store files).
@throws IOException When the IO operations fail.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java