/* The rollback segment memory object */
struct trx_rseg_t{
/**********************************************************/
ulint id; /*!rollback segment id == the index of its slot in the trx system file copy */
ulint space; /*!space where the rollback segment is header is placed */
ulint page_no;/* page number of the rollback segment header ,即slot所在页页号*/
/*--------------------------------------------------------*/
/* Fields for update undo logs */
UT_LIST_BASE_NODE_T(trx_undo_t) update_undo_list;
/* List of update undo logs */
UT_LIST_BASE_NODE_T(trx_undo_t) update_undo_cached;
/* List of update undo log segments
cached for fast reuse */
/*--------------------------------------------------------*/
/* Fields for insert undo logs */
UT_LIST_BASE_NODE_T(trx_undo_t) insert_undo_list;
/* List of insert undo logs */
UT_LIST_BASE_NODE_T(trx_undo_t) insert_undo_cached;
/* List of