ActiveRecord tries to do this on update_attributes call

returned.sql

SELECT 1 FROM `models` WHERE 
(`models`.`id` = BINARY 'd178546e-39bc-11e2-8b8b-40406f66ce3e' 
  AND `models`.`id` != 'd178546e-39bc-11e2-8b8b-40406f66ce3e') LIMIT 1

schema

create_table "models", :id => false, :force => true do |t|                                                                                                                                      
    t.datetime "scheduled_on"                                                                                                                                                                             
    t.datetime "responded_on"                                                                                                                                                                             
    t.integer  "respondent_id"                                                                                                                                                                            
    t.datetime "created_at",                                          :null => false                                                                                                                      
    t.datetime "updated_at",                                          :null => false                                                                                                                      
    t.string   "survey_instance_id", :limit => 36                                                                                                                                                         
    t.string   "id",                 :limit => 36                                                                                                                                                          
    t.string   "moment_type"                                                                                                                                                                              
    t.boolean  "outside_schedule"                                                                                                                                                                         
    t.datetime "edited_at"                                                                                                                                                                                
    t.boolean  "on_device",                        :default => false                                                                                                                                      
    t.integer  "user_id"                                                                                                                                                                                  
  end     

add_index "random_moments", ["id"], :name => "index_random_moments_on_id"                                                                                                                               
  add_index "random_moments", ["id"], :name => "random_moments_id_unique", :unique => true                                                                                                                
  add_index "random_moments", ["respondent_id"], :name => "index_random_moments_on_respondent_id"                                                                                                         
  add_index "random_moments", ["survey_instance_id"], :name => "index_random_moments_on_survey_instance_id"