anchor.diff:  
   The `host` parameter must contain a scheme, host, and port (e.g.
   `https://otherhost:9200`). The `username` and `password` parameters are
  -optional and when they are present reindex will connect to the remote
  +optional, and when they are present `_reindex` will connect to the remote
   Elasticsearch node using basic auth. Be sure to use `https` when using
   basic auth or the password will be sent in plain text.
   
  
positive.code: ===== Picking the number of slices
  
  If slicing automatically, setting `slices` to `auto` will choose a reasonable
  number for most indices. If you're slicing manually or otherwise tuning
  automatic slicing, use these guidelines.
  
  Query performance is most efficient when the number of `slices` is equal to the
  number of shards in the index. If that number is large, (for example,
  500) choose a lower number as too many `slices` will hurt performance. Setting
  `slices` higher than the number of shards generally does not improve efficiency
  and adds overhead.
  
  
negative.code: // CONSOLE
  // TEST[setup:big_twitter]
  
  <1> `_reindex` defaults to sorting by `_doc` so `random_score` will not have any
  effect unless you override the sort to `_score`.
  