公司做网站需要哪些资料,免费设计在线生成,网站怎么备案,网站价值评估 php事务结构 struct trx_t 写在前面 InnoDB是MySQL的一个存储引擎#xff0c;支持事务#xff0c;支持非堵塞的一致性读#xff0c;物理存储结构是Page#xff0c;每个事务都有回滚日志#xff0c;重做日志#xff0c;事务还会有死锁检测#xff0c;各种各样不同的锁等等等… 事务结构 struct trx_t 写在前面 InnoDB是MySQL的一个存储引擎支持事务支持非堵塞的一致性读物理存储结构是Page每个事务都有回滚日志重做日志事务还会有死锁检测各种各样不同的锁等等等等 翻看innodb的源码发现数下来开启一个事务的时候InnoDB需要处理63个变量变量类型纷繁复杂结构体自定义的数据类型等等。 这次整理我翻看了不少同行们写的博客包括InnoDB官方博客有一个心得是不同人的翻译不一样尽管是官方写的博客也会因为一些篇幅问题减掉了一些细节的介绍。这次的整理我特意保留了原来的英文备注然后加上自己的理解进去。 MySQL的源码文件很多InnoDB也不少不过我觉得事务的结构体代码还是要理解透的透了才能理解透事务的实现细节更加深入认识数据库系统为了保证数据的一致性做了多少事情.... 文件地址 文件地址 storage/innobase/include/trx0trx.h 变量1 magic_n 变量类型 ulint #define ulint unsigned long 变量2 mutex 变量类型 ib_mutex_t mutex的代码备注 Mutex protecting the fields state and lock (except some fields of lock, which are protected by lock_sys-mutex) Mutex保护字段的状态和锁定除了某些锁定字段由lock_sys- mutex保护 ib_mutex_t对应的结构体 /** InnoDB mutex */
struct ib_mutex_t {os_event_t event; /*! Used by sync0arr.cc for the wait queue */volatile lock_word_t lock_word; /*! lock_word is the targetof the atomic test-and-set instruction whenatomic operations are enabled. */ 这里面又有另外一个结构体 os_event_t /** An asynchronous signal sent between threads */
struct os_event {
#ifdef __WIN__HANDLE handle; /*! kernel event object, slow,used on older Windows */
#endifos_fast_mutex_t os_mutex; /*! this mutex protects the nextfields */ibool is_set; /*! this is TRUE when the event isin the signaled state, i.e., a threaddoes not stop if it tries to wait forthis event */ib_int64_t signal_count; /*! this is incremented each timethe event becomes signaled */os_cond_t cond_var; /*! condition variable is used inwaiting for the event */UT_LIST_NODE_T(os_event_t) os_event_list;/*! list of all created events */
}; 变量3 state 变量类型 trx_state_t 变量备注 事务状态TRX_STATE_NOT_STARTED TRX_STATE_ACTIVE TRX_STATE_PREPARED TRX_STATE_COMMITTED_IN_MEMORY (alias below COMMITTED) 结构体trx_state_t的源码 /** Transaction states (trx_t::state) */
enum trx_state_t {TRX_STATE_NOT_STARTED,TRX_STATE_ACTIVE,TRX_STATE_PREPARED, /* Support for 2PC/XA */TRX_STATE_COMMITTED_IN_MEMORY
}; 变量4 lock 变量类型 trx_lock_t 变量备注 Information about the transaction locks and state. Protected by trx-mutex or lock_sys-mutex or both 事务锁和状态有关的信息。 受trx- mutex或lock_sys- mutex或两者保护 trx_lock_t的结构体定义 struct trx_lock_t {ulint n_active_thrs; /*! number of active query threads */trx_que_t que_state; /*! valid when trx-state TRX_STATE_ACTIVE: TRX_QUE_RUNNING,TRX_QUE_LOCK_WAIT, ... */lock_t* wait_lock; /*! if trx execution state isTRX_QUE_LOCK_WAIT, this points tothe lock request, otherwise this isNULL; set to non-NULL when holdingboth trx-mutex and lock_sys-mutex;set to NULL when holdinglock_sys-mutex; readers shouldhold lock_sys-mutex, except whenthey are holding trx-mutex andwait_lockNULL */ib_uint64_t deadlock_mark; /*! A mark field that is initializedto and checked against lock_mark_counterby lock_deadlock_recursive(). */ibool was_chosen_as_deadlock_victim;/*! when the transaction decides towait for a lock, it sets this to FALSE;if another transaction chooses thistransaction as a victim in deadlockresolution, it sets this to TRUE.Protected by trx-mutex. */time_t wait_started; /*! lock wait started at this time,protected only by lock_sys-mutex */que_thr_t* wait_thr; /*! query thread belonging to thistrx that is in QUE_THR_LOCK_WAITstate. For threads suspended in alock wait, this is protected bylock_sys-mutex. Otherwise, this mayonly be modified by the thread that isserving the running transaction. */mem_heap_t* lock_heap; /*! memory heap for trx_locks;protected by lock_sys-mutex */UT_LIST_BASE_NODE_T(lock_t)trx_locks; /*! locks requestedby the transaction;insertions are protected by trx-mutexand lock_sys-mutex; removals areprotected by lock_sys-mutex */ib_vector_t* table_locks; /*! All table locks requested by thistransaction, including AUTOINC locks */ibool cancel; /*! TRUE if the transaction is beingrolled back either via deadlockdetection or due to lock timeout. Thecaller has to acquire the trx_t::mutexin order to cancel the locks. Inlock_trx_table_locks_remove() wecheck for this cancel of a transactionslocks and avoid reacquiring the trxmutex to prevent recursive deadlocks.Protected by both the lock sys mutexand the trx_t::mutex. */
}; 变量5 is_recovered 变量类型 ulint 变量备注 0normal transaction, 1recovered, must be rolled back, protected by trx_sys-mutex when trx-in_rw_trx_list holds 0 正常事务1 恢复必须回滚当trx- in_rw_trx_list保持时由trx_sys- mutex保护 变量6 op_info 变量类型 const char* 变量7 isolation_level 变量类型 ulint 变量备注 READ UNCOMMITTED,READ COMMITTED,REPEATABLE READ,SERIALIZABLE 变量8 is_registered:1 变量类型 unsigned 变量备注 MySQL has a transaction coordinator to coordinate two phase commit between multiple storage engines and the binary log. When an engine participates in a transaction, its responsible for registering itself using the trans_register_ha() API. This flag is set to 1 after the transaction has been registered with the coordinator using the XA API, and is set to 0 after commit or rollback MySQL有一个事务协调器来协调多个存储引擎和二进制日志之间的两阶段提交,它负责使用trans_register_haAPI注册自己. 在事务已使用XA API向协调器注册后此标志设置为1并在提交或回滚后设置为0 变量9 check_unique_secondary 变量类型 ulint 变量备注 通常为TRUE但是如果用户想要通过抑制对二级索引的唯一键检查来加快插入当我们决定是否可以为它们使用插入缓冲区时我们设置这个FALSE 变量10 support_xa 变量类型 ulint 变量备注 normally we do the XA two-phase commit steps, but by setting this to FALSE, one can save CPU time and about 150 bytes in the undo log size as then we skip XA steps 通常我们做XA两阶段提交步骤,但通过设置为FALSE,可以节省CPU时间和大约150字节的undo日志大小然后我们跳过XA步骤 变量11 flush_log_later 变量类型 ulint 变量备注 In 2PC, we hold the prepare_commit mutex across both phases. In that case, we defer flush of the logs to disk until after we release the mutex 在两阶段提交我们持有两个阶段的prepare_commit互斥体。 在这种情况下我们推迟刷新日志到磁盘直到我们释放互斥体。 变量12 must_flush_log_later 变量类型 ulint 变量备注 this flag is set to TRUE in trx_commit() if flush_log_later was TRUE, and there were modifications by the transaction; in that case we must flush the log in trx_commit_complete_for_mysql() 此标志在trx_commit中设置为TRUE如果flush_log_later为TRUE并且事务进行了修改 在这种情况下我们必须通过trx_commit_complete_for_mysql刷新日志 变量13 duplicates 变量类型 ulint 变量备注 TRX_DUP_IGNORE | TRX_DUP_REPLACE 变量14 has_search_latch 变量类型 ulint 变量备注 TRUE if this trx has latched the search system latch in S-mode 如果此trx已在S模式下锁定搜索系统锁存器则为TRUE 变量15 search_latch_timeout 变量类型 ulint 变量备注 If we notice that someone is waiting for our S-lock on the search latch to be released, we wait in row0sel.cc for BTR_SEA_TIMEOUT new searches until we try to keep the search latch again over calls from MySQL; this is intended to reduce contention on the search latch 如果我们注意到有事务在等待我们的S锁锁定被释放我们在row0sel.cc中等待BTR_SEA_TIMEOUT新的搜索直到我们尝试保持搜索锁定再次超过来自MySQL的调用; 这旨在减少对搜索锁存器的争用 变量16 dict_operation 变量类型 trx_dict_op_t 变量备注 主要是三种状态 没有修改表结构0 改表1 修改索引2 /** Type of data dictionary operation */
enum trx_dict_op_t {/** The transaction is not modifying the data dictionary. */TRX_DICT_OP_NONE 0,/** The transaction is creating a table or an index, ordropping a table. The table must be dropped in crashrecovery. This and TRX_DICT_OP_NONE are the only possibleoperation modes in crash recovery. */TRX_DICT_OP_TABLE 1,/** The transaction is creating or dropping an index in anexisting table. In crash recovery, the data dictionarymust be locked, but the table must not be dropped. */TRX_DICT_OP_INDEX 2
}; 变量17 declared_to_be_inside_innodb 变量 ulint 备注 this is TRUE if we have declared this transaction in srv_conc_enter_innodb to be inside the InnoDB engine 如果我们已经在srv_conc_enter_innodb中声明这个事务在InnoDB引擎中那么这是TRUE 变量18 n_tickets_to_enter_innodb 变量类型 ulint 变量备注 this can be 0 only when declared_to_... is TRUE; when we come to srv_conc_innodb_enter, if the value here is 0, we decrement this by 1 这可以 0只有当declared_to_be_inside_innodb _…为TRUE 当我们来到srv_conc_innodb_enter如果这里的值 0我们将其减1 变量19 dict_operation_lock_mode 变量类型 ulint 变量备注 0, RW_S_LATCH, or RW_X_LATCH: the latch mode trx currently holds on dict_operation_lock. Protected by dict_operation_lock 0RW_S_LATCH或RW_X_LATCH锁存模式trx当前持有dict_operation_lock。 受dict_operation_lock保护 变量20 no 变量类型 trx_id_t storage/innobase/include/univ.i
typedef ib_uint64_t ib_id_t;storage/innobase/include/trx0types.h
/** Transaction identifier (DB_TRX_ID, DATA_TRX_ID) */
typedef ib_id_t trx_id_t; 变量备注 transaction serialization number: max trx id shortly before the transaction is moved to COMMITTED_IN_MEMORY state. Protected by trx_sys_t::mutex when trx-in_rw_trx_list. Initially set to TRX_ID_MAX 事务序列号事务被移动到COMMITTED_IN_MEMORY状态之前不久的max trx id。 当trx- in_rw_trx_list时由trx_sys_t :: mutex保护。 最初设置为TRX_ID_MAX 变量21 start_time 变量类型 time_t 变量备注 time the trx state last time became TRX_STATE_ACTIVE trx状态变为TRX_STATE_ACTIVE的上一次时间开始时间 变量22 id 变量类型 trx_id_t 变量备注 transaction id 事务id 变量23 XID 变量类型 XID sql/handler.h
typedef struct xid_t XID; xid_t是一个结构体代码太多这里就不贴了 变量备注 X/Open XA transaction identification to identify a transaction branch 打开分布式事务的标识以便区分事务分支 变量24 commit_lsn 变量类型 /* Type used for all log sequence number storage and arithmetics */
typedef ib_uint64_t lsn_t; 变量备注 lsn at the time of the commit lsn提交的时间 变量25 table_id 变量类型 table_id_t 变量备注 Table to drop iff dict_operation TRX_DICT_OP_TABLE, or 0 变量26 mysql_thd 变量类型 THD* 这是一个超级大的结构体详情需要看代码 变量备注 MySQL thread handle corresponding to this trx, or NULL 对应这个trx的MySQL线程句柄或NULL 变量27 mysql_log_file_name 变量类型 const char* 变量备注 if MySQL binlog is used, this field contains a pointer to the latest file name; this is NULL if binlog is not used 如果使用MySQL binlog此字段包含指向最新文件名的指针; 如果不使用binlog则为NULL 变量28 mysql_log_offset 变量类型 ib_int64_t 变量备注 if MySQL binlog is used, this field contains the end offset of the binlog entry 如果使用MySQL binlog则此字段包含binlog条目的结束偏移量 变量29 n_mysql_tables_in_use 变量类型 ulint 变量备注 number of Innobase tables used in the processing of the current SQL statement in MySQL MySQL中处理当前SQL语句时使用的Innobase表的数量 变量30 mysql_n_tables_locked 变量类型 ulint 变量备注 how many tables the current SQL statement uses, except those in consistent read 变量31 trx_list 变量类型 UT_LIST_NODE_T(trx_t) #define UT_LIST_NODE_T(TYPE) \
struct { \TYPE* prev; /*! pointer to the previous node, \NULL if start of list */ \TYPE* next; /*! pointer to next node, NULL if end of list */\
} 变量备注 list of transactions; protected by trx_sys-mutex. The same node is used for both trx_sys_t::ro_trx_list and trx_sys_t::rw_trx_list 事务列表受trx_sys-mutex保护。 同样的节点用于trx_sys_t :: ro_trx_list和trx_sys_t :: rw_trx_list 变量32 mysql_trx_list 变量类型 UT_LIST_NODE_T(trx_t) 变量备注 list of transactions created for MySQL; protected by trx_sys-mutex 变量33 error_state 变量类型 dberr_t 变量备注 0 if no error, otherwise error number; NOTE That ONLY the thread doing the transaction is allowed to set this field: this is NOT protected by any mutex 错误码 注意只有执行事务的线程才允许设置此字段 这不受任何互斥保护 变量34 dict_index_t*error_info 变量类型 const 变量备注 if the error number indicates a duplicate key error, a pointer to the problematic index is stored here 如果错误号表示重复键错误则在此存储指向有问题索引的指针 变量35 error_key_num 变量类型 ulint 变量备注 if the index creation fails to a duplicate key error, a mysql key number of that index is stored here 如果索引创建失败重复的键错误该索引的mysql键号存储在这里 变量36 sess 变量类型 sess_t* /* The session handle. This data structure is only used by purge and is
not really necessary. We should get rid of it. */
struct sess_t{ulint state; /*! state of the session */trx_t* trx; /*! transaction object permanentlyassigned for the session: thetransaction instance designated by thetrx id changes, but the memorystructure is preserved */UT_LIST_BASE_NODE_T(que_t)graphs; /*! query graphs belonging to thissession */
}; 变量备注 session of the trx, NULL if none 变量37 graph 变量类型que_t* 变量备注 query currently run in the session, or NULL if none; NOTE that the query belongs to the session, and it can survive over a transaction commit, if it is a stored procedure with a COMMIT WORK statement, for instance 查询当前在运行中的会话如果没有则为NULL 注意查询属于会话并且它可以通过事务提交存活如果它是具有COMMIT WORK语句的存储过程例如 变量38 global_read_view_heap 变量类型 mem_heap_t* /* A memory heap is a nonempty linear list of memory blocks */
typedef mem_block_t mem_heap_t;/* A block of a memory heap consists of the info structure
followed by an area of memory */
typedef struct mem_block_info_t mem_block_t;mem_block_info_t又是一个复杂的结构体 变量备注 memory heap for the global read view 内存堆的全局读取视图 变量39 global_read_view 变量类型 read_view_t* 又是一个比较复杂的结构体 一致的读取视图关联到事务或NULL 变量40 read_view 变量类型 read_view_t* 变量备注 consistent read view used in the transaction or NULL, this read view if defined can be normal read view associated to a transaction (i.e. same as global_read_view) or read view associated to a cursor 一致的读取视图用于事务或NULL此读取视图如果定义可以是与事务相关联的正常读取视图即与global_read_view相同或与光标相关联的读取视图 变量41 trx_savepoints 变量类型 UT_LIST_BASE_NODE_T(trx_named_savept_t) 变量备注 savepoints set with SAVEPOINT ..., oldest first 使用SAVEPOINT设置保存点的列表 ...最旧的放在最前面 变量42 undo_mutex 变量类型 ib_mutex_t 变量备注 mutex protecting the fields in this section (down to undo_no_arr), EXCEPT last_sql_stat_start, which can be accessed only when we know that there cannot be any activity in the undo logs! 互斥体保护此部分中的字段向下到undo_no_arr除了 last_sql_stat_start只有当我们知道在撤销日志中不能有任何活动时才可以访问它们 变量43 undo_no 变量类型undo_no_t /** Undo number */
typedef ib_id_t undo_no_t; 变量备注 next undo log record number to assign; since the undo log is private for a transaction, this is a simple ascending sequence with no gaps; thus it represents the number of modified/inserted rows in a transaction 分配下一个撤销日志记录号; 因为撤销日志对于事务是私有的这是一个没有间隙的简单升序序列; 因此它表示事务中修改/插入行的数量。 变量44 last_sql_stat_start 变量类型 trx_savept_t 变量备注 undo_no when the last sql statement was started: in case of an error, trx is rolled back down to this undo number; see note at undo_mutex 当最后一个sql语句启动时分配undo_no在出现错误的情况下trx被回滚到这个撤销号; 请参见undo_mutex中的注释 变量45 rseg 变量类型 trx_rseg_t* 这又是一个比较复杂的结构体但segement其实是和Page绑定在一起的 变量备注 rollback segment assigned to the transaction, or NULL if not assigned yet 回滚段分配给事务如果尚未分配则为NULL 变量46 insert_undo 变量类型 trx_undo_t* 变量备注 pointer to the insert undo log, or NULL if no inserts performed yet 指向插入undo日志的指针如果尚未执行插入则为NULL 变量47 update_undo 变量类型 trx_undo_t* 变量备注 pointer to the update undo log, or NULL if no update performed yet 变量48 roll_limit 变量类型 undo_no_t 变量备注 least undo number to undo during a rollback 事务回滚的时候最小的回滚数 变量49 pages_undone 变量类型 ulint 变量备注 number of undo log pages undone since the last undo log truncation 自上次撤消日志截断以来撤销日志页面的数量 变量50 undo_no_arr 变量类型 trx_undo_arr_t* 变量备注 array of undo numbers of undo log records which are currently processed by a rollback operation 撤消日志记录的撤销编号数组这些撤消日志记录当前由回滚操作处理 变量51 n_autoinc_rows 变量类型ulint 变量备注 no. of AUTO-INC rows required for an SQL statement. This is useful for multi-row INSERTs SQL语句所需的AUTO-INC行的数量。 这对于多行INSERT非常有用 变量52 autoinc_locks 变量类型 ib_vector_t* 变量备注 AUTOINC locks held by this transaction. Note that these are also in the lock list trx_locks. This vector needs to be freed explicitly when the trx instance is destroyed. Protected by lock_sys-mutex 此事务持有的AUTOINC锁。 注意这些也在锁定列表trx_locks中。 当trx实例被销毁时这个向量需要被明确地释放。 受lock_sys- mutex保护 变量53 read_only 变量类型 ibool 变量备注 TRUE if transaction is flagged as a READ-ONLY transaction. if !auto_commit || will_lock 0 then it will added to the list trx_sys_t::ro_trx_list. A read only transaction will not be assigned an UNDO log. Non-locking auto-commit read-only transaction will not be on either list 如果事务标记为READ-ONLY事务则为TRUE。 ifauto_commit || will_lock 0那么它将被添加到列表trx_sys_t :: ro_trx_list。 只读事务将不会被分配UNDO日志。 非锁定自动提交只读事务将不在任一列表上 变量54 auto_commit 变量类型 ibool 变量备注 TRUE if it is an autocommit 变量55 will_lock 变量类型 ulint 变量备注 Will acquire some locks. Increment each time we determine that a lock will be acquired by the MySQL layer 标记会获得一些锁。 每次我们确定需要获取锁的时候将被MySQL层获取时递增 变量56 ddl 变量类型 bool 变量备注 true if it is a transaction that is being started for a DDL operation 如果它是为DDL操作启动的事务则为true 变量57 fts_trx 变量类型 fts_trx_t* 变量类型 FTS information, or NULL if transaction hasnt modified tables with FTS indexes (yet) FTS信息如果事务尚未修改具有FTS索引的表尚未则为NULL; 变量58 fts_next_doc_id 变量类型 doc_id_t 变量备注 The document id used for updates 用于更新的文档ID 变量59 flush_tables 变量类型 ulint 变量备注 if covering the FLUSH TABLES,count of tables being flushed 如果“覆盖”FLUSH TABLES“则表的计数被刷新 变量60 api_trx 变量类型 bool 变量备注 trx started by InnoDB API 变量61 api_auto_commit 变量类型 bool 变量备注 automatic commit 变量62 read_write 变量类型 bool 变量备注 if read and write operation 变量63 detailed_error[256] 变量类型char 变量备注 detailed error message for last error, or empty
