A tale of Upsert issues

measurement_datum.rb

class MeasurementDatum
  belongs_to :measurement_point
  # Schema
  # - measurement_point_id, integer
  # - recorded_at, datetime
  # - value, double
end

measurement_point.rb

require 'csv'

class MeasurementPoint
  has_many :measurement_point
  # Schema
  # - id, integer
  # - title, string
  
  # Imports a csv of data
  # expected to have header columns mapping to recorded_at, value
  # 
  # @param [String] csv
  # @return [Array<MeasurementDatum>]
  def import_csv(csv)
    csv = CSV.parse(csv, headers: true,  converters: :numeric)
    return unless (%w(recorded_at value) - csv.headers).empty?
    
    csv.each do |row|
      MeasurementDatum.upsert({ measurement_point_id: id, recorded_at: row['recorded_at'] },value: row['value'].to_f)
    end
  end
end