Remove constant fields

metadata.json

{
  "name": "Remove constant fields",
  "kind": "script",
  "description": "Remove fields that are constant",
  "source_code": "script.whizzml",
  "imports":[
    ],
  "inputs":[
    {
      "name": "input-dataset",
      "type": "dataset-id",
      "description": "The dataset to clean up"
    },
    {
      "name": "keep-datetimes?",
      "type": "boolean",
      "default": false,
      "description": "Whether to keep datetime fields (removed by default)"
    }],
  "outputs":[
    {
      "name": "dataset",
      "type": "dataset-id",
      "description": "The cleaned up dataset"
    }]
}

script.whizzml

(define (clean-up ds-id)
  (let (fds (resource-fields ds-id)
        fds (map (lambda (id f) (assoc f "id" id)) (keys fds) (values fds))
        cf? (lambda (fd)
              (and (or (not (datetime-field? fd))
                       (not keep-datetimes?))
                   (< (count (field-distribution fd)) 2)))
        excl (map (lambda (f) (f "id")) (filter cf? fds)))
    (wait (create-dataset ds-id {"excluded_fields" excl}))))

(define dataset (clean-up input-dataset))