innodb purge--聚集索引

row_purge_remove_clust_if_poss_low
    if(node->roll_ptr != row_get_rec_roll_ptr(rec, index, offsets)) {
         /*Someone else has modified the record later: do not remove */
         gotofunc_exit;
    }
    if(mode == BTR_MODIFY_LEAF) {
         success= btr_cur_optimistic_delete(btr_pcur_get_btr_cur(&node->pcur),0, &mtr);
    }else {
         btr_cur_pessimistic_delete(&err,FALSE, btr_pcur_get_btr_cur(&node->pcur), 0,RB_NONE,&mtr);
    }