Unknown field [missing] in terms in transforms

[akleandrov]

"reason": "[1:500] [data_frame_terms_group] unknown field [missing], parser not found"

PUT _data_frame/transforms/testconc
{
  "source": {
    "index": "from"
  },
  "pivot": {
    "group_by": {
      "period": {
        "terms": {
          "field": "period"
        }
      },
      "nullablefield": {
        "terms": {
          "field": "myfield",
          "missing": "n/a"
        }
      }
    },
    "aggregations": {
      "u": {
        "sum": {
          "field": "u"
        }
      }
    }
  },
  "dest": {
    "index": "trindex"
  },
  "frequency": "5m",
  "sync": {
    "time": {
      "field": "createdAt",
      "delay": "30s"
    }
  }
}

ES 7.4 (original elasticsearch image)

[elasticmachine]

Pinging @elastic/ml-core (:ml/Transform)

[benwtrent]

@akleandrov missing is currently not supported in transforms. But it seems like a good enhancement.

[akleandrov]

@benwtrent However, the documentation does not indicate that the terms in transformations work with restrictions. Will this be supported in the future?

[benwtrent]

@akleandrov transforms is built on top of Composite Aggregations.

From what I can tell, missing is not currently supported in Composite aggregations. So, it might take some time before we see it supported in transforms.