Currently the supported column types in Druid adapter are: LONG, DOUBLE, STRING and hyperUnique
There's no clue to show Druid has DOUBLE as its column type. But instead it should be FLOAT as mentioned in Druid Documentation:
Dimension columns will have type STRING. Metric columns will have type FLOAT or LONG or name of the underlying complex type such as hyperUnique in case of COMPLEX metric. Timestamp column will have type LONG.