anchor.diff:  Just as in <<docs-update,Update API>> you can set `ctx.op` to change the
   operation that is executed:
   
  -
  +[horizontal]
   `noop`::
   
   Set `ctx.op = "noop"` if your script decides that it doesn't have to make any
  
positive.code: [[docs-update-by-query-automatic-slice]]
  ==== Automatic slicing
  
  You can also let update-by-query automatically parallelize using
  <<sliced-scroll>> to slice on `_id`. Use `slices` to specify the number of
  slices to use:
  
  
negative.code: --------------------------------------------------
  // TESTRESPONSE
  
  <1> This object contains the actual status. It is just like the response JSON
  with the important addition of the `total` field. `total` is the total number
  of operations that the reindex expects to perform. You can estimate the
  progress by adding the `updated`, `created`, and `deleted` fields. The request
  