using redis to reserve a set of records from a larger group

snippet.rb

def find_for_curation(conditions, user_id)
  RedisConnection.db.sadd('curators', user_id)
  RedisConnection.db.del("curator-#{user_id}")
  curator_ids = RedisConnection.db.smembers('curators')
  curator_keys = curator_ids.map { |id| "curator-#{id}" }
  active_annotation_ids = RedisConnection.db.sunion(*curator_keys)
  annotations = Annotation.where(conditions).where("annotations.id NOT IN (#{active_annotation_ids.to_in_query_string})").joins(:ontology_term).joins(:ontology).limit(15).order('ontology_terms.name')
  annotations.each do |annotation|
    RedisConnection.db.sadd("curator-#{user_id}", annotation.id)
  end
  RedisConnection.db.expire("curator-#{user_id}", 300)
  annotations
end