anchor.diff:  --------------------------------------------------
   // TESTRESPONSE[s/"took" : 147/"took" : "$body.took"/]
   
  +[horizontal]
   `took`::
   
   The number of milliseconds from start to end of the whole operation.
  
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 `_uid`. Use `slices` to specify the number of
  slices to use:
  
  
negative.code: 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
  