gistfile1.rb

class SearchSession < ActiveRecord::Base
  include Redis::Objects
  
  belongs_to :user
  validates :user_id, :presence => true
  
  serialize :conditions, Hash
  
  list      :cached_results_ids
  
  after_save :prune_cache
  
  NUM_CACHE_RESULTS = 500
  
  def results
    SearchSessionResultSet.new(result_ids)
  end
  
  def result_ids
    # Check if cached IDs exist, return collection of these
    # Fetch IDs from ES
    # Cache IDs
    # Return collection
    unless self.cached_results_ids.any?
      hits = User.search_hits({:match_all => true}, {:fields => '_id', :size => NUM_CACHE_RESULTS}) # Only fetch _id field from ElasticSearch
      hits.each do |hit|
        self.cached_results_ids << hit.id
      end
    end
    
    self.cached_results_ids
  end
  
  def clear!
    self.cached_results_ids.clear
  end
  
  private
  
  def prune_cache
    clear! if conditions_changed?
  end
end

######### SearchSessionResultSet ####

class SearchSessionResultSet < Array
  def initialize(ids)
    @ids        = ids
    @users      = []
    @populated  = false
  end
  
  def before_any_array_method(method, *args)
    fill_users_array_according_to_method_and_args
    @users.send(method, *args)
  end
end