in connector/src/main/scala/com/microsoft/kusto/spark/utils/DataTypeMapping.scala [61:66]
def getSparkTypeToKustoTypeMap(fieldType: DataType): String = {
if (fieldType.isInstanceOf[DecimalType]) "decimal"
else if (fieldType.isInstanceOf[ArrayType] || fieldType.isInstanceOf[StructType] || fieldType
.isInstanceOf[MapType]) "dynamic"
else DataTypeMapping.SparkTypeToKustoTypeMap.getOrElse(fieldType, "string")
}