InnoDB unnecessarily commits mtr during secondary index search to preserve clustered index latching order

dberr_t                                                                         

row_search_mvcc(...)                                                            

{                                                                               

...                                                                             

        } else if (mtr_has_extra_clust_latch) {                                 

                /* If we have extra cluster latch, we must commit               

                mtr if we are moving to the next non-clustered                  

                index record, because we could break the latching               

                order if we would access a different clustered                  

                index page right away without releasing the previous. */        

                btr_pcur_store_position(pcur, &mtr);                            

                mtr.commit();                                                   

                mtr_has_extra_clust_latch = FALSE;                              

                mtr.start();                                                    

                if (sel_restore_position_for_mysql(&same_user_rec,              

                                                   BTR_SEARCH_LEAF,             

                                                   pcur, moves_up, &mtr)) {     

                        goto rec_loop;                                          

                }                                                               

        }                                                                       

...                                                                             

}