When running a segmentMetadata query I get the following results back:

      "revenue_hist": {
        "type": "STRING",
        "size": -1,
        "cardinality": null,
        "errorMessage": "error:noSizeFn"
      },
      ...
      "unique_visitors": {
        "type": "STRING",
        "size": -1,
        "cardinality": null,
        "errorMessage": "error:noSizeFn"
      },

One of those columns is a hyperLogLog and the other an aproxHistogram (guess which is which).
By checking the errorMessage == "error:noSizeFn" (which seems to be unique to hyperLogLog and aproxHistogram columns) I can determine that both of those columns are ether hyperLogLog or aproxHistogram. I would like there to be a way to actually tell them apart without making another query.

In general it would be great to be able to see the aggregate function that rolled up the metrics.