importer.rb

class Importer
  CONN = ActiveRecord::Base.connection
  F = "00F"
  I = "00I"

  def extract_to_database(collection) # collection is a file
    add       = true
    tmp       = []
    type      = F
    inserts   = []
    f         = []

    collection.each_with_index do |line, i|
      _type    = line.strip
      _changed = [F,I].include? _type

      if _changed && i > 0
        case type
        when F then f << tmp
        when I
          inserts.push "(#{tmp[1]},'#{tmp[2]}','#{tmp[3]}')"
        end

        tmp  = []
        type = _type
      end

      tmp << line
    end
    sql = "INSERT INTO products (`code`, `name`, `price`) VALUES #{inserts.join(", ")}"
    CONN.execute sql
  end
end

Check a refactor in my fork of the gist. Note that "f" is not used anywhere so I removed it. I used a model Product, if you are using AR it makes no sense to use raw SQL. The key to make it functional is using each_slice.