Carrierwave upload directory partitioning

carrierwave-upload-partitioning.rb

# thanks to @rainchen
class BaseUploader < CarrierWave::Uploader::Base
 
  storage :file
  after :remove, :delete_empty_upstream_dirs
 
  # e.g.: "uploads/venue/photo/000/000/003/thumb_Limoni_-_overall-resized-1.jpg"
  def store_dir
    "#{base_store_dir}/#{model_id_partition}"
  end
 
  def base_store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}"
  end
 
  # e.g.: 1234 => "000/001/234"
  def model_id_partition
    ("%09d" % model.id).scan(/\d{3}/).join("/")
  end
 
  # tips: https://github.com/jnicklas/carrierwave/wiki/How-to%3A-Make-a-fast-lookup-able-storage-directory-structure
  def delete_empty_upstream_dirs
    # path = ::File.expand_path(store_dir, root)
    # Dir.delete(path) # fails if path not empty dir
 
    # delete partition dir
    # e.g.: "111/222/333" => [["111", "222", "333"], ["111", "222"], ["111"]]
    id_partitions = model_id_partition.split('/').inject([]) { |_, i| _ << ((_.last || []).dup << i.dup).flatten }.reverse
    partition_dirs = id_partitions.map { |_| "#{base_store_dir}/#{_.join("/")}" }
    
    [*partition_dirs, base_store_dir].each do |_path|
      path = ::File.expand_path(_path, root)
      # debugger if base_store_dir = "uploads/venue/photo"
      Dir.delete(path) # fails if path not empty dir, beware ".DS_Store" when in development
    end
  rescue SystemCallError
    true # nothing, the dir is not empty
  end
 
end