i'm oddly proud of this

gistfile1.rb

  desc "seperate medium and surface product properties"
  task :seperate_medium_and_surface_properties => :environment do
    medium_property_id = Property.find_by_name("Medium").id
    if Property.find_by_name("Surface")
      surface_property_id = Property.find_by_name("Surface").id
    else
      Property.create(name: "Surface", presentation: "Surface")
      surface_property_id = Property.find_by_name("Surface").id
    end

    actionable_properties = ProductProperty.where(property_id: medium_property_id)

    actionable_properties.find_each do |prop|
      product_id = prop.product_id
      # search for " on " with spaces to make it easier, returns an array ["Oil", " on ", "Canvas"] for example
      value_array = prop.value.rpartition(" on ") if prop.value
      if value_array && value_array.include?(" on ")
        # update medium to single word
        prop.update_attribute(:value, value_array[0])
        # create surface property
        ProductProperty.create(product_id: product_id, property_id: surface_property_id, value: value_array[2])
      else
        prop.product.data_errors.new(message: "ProductProperty for Medium needs a review") if prop.product
      end
    end
  end

Don't create Property if it already exists

ProductProperty.where(property_id: medium_property_id) One big sql call instead of calling all and iterating through them. How many are there? We might need to iterate through them with find each. So ProductProperty.where().find_each do |prop|

like the rpartition
about if value_array.includes("on") or some sort of array search. What if it's Acrylic Paint On Canvas. Your index 1 look up will miss. When you find the on, everything before it goes into medium and after goes into surface