Distributed Transaction Processing: The XA Specification
mysql XA Transactions
oracle 10g
mysql xa 例子
X/Open XA distributed transactions
SHOW ENGINES/G
查看是否支持innodb
use test;
CREATE TABLE aa(a INT, b CHAR (20), INDEX (a)) ENGINE=InnoDB;
xa begin 'abc','def',7;
insert into aa values(1, 'a');
xa end 'abc','def',7;
xa prepare 'abc','def',7;
xa commit 'abc','def',7;
xa rollback 'abc','def',7;
xa recover;
prepare 之后 recover 才能看到结果
xid在内部的定义
/** X/Open XA distributed transaction identifier */
struct xid_t {
long formatID; /*!< format identifier; -1
means that the XID is null */
long gtrid_length; /*!< value from 1 through 64 */
long bqual_length; /*!< value from 1 through 64 */
char data[XIDDATASIZE]; /*!< distributed transaction
identifier */
};
//在事务结构体中增加了一项
struct trx_struct{
XID xid; /*!< X/Open XA transaction
identification to identify a transaction branch */
}
enum xa_states {XA_NOTR=0, XA_ACTIVE, XA_IDLE, XA_PREPARED, XA_ROLLBACK_ONLY};
//begin 置为XA_ACTIVE, end置为 XA_IDLE
extern const char *xa_state_names[];
typedef struct st_xid_state {
/* For now, this is only used to catch duplicated external xids */
XID xid; // transaction identifier
enum xa_states xa_state; // used by external XA only
bool in_thd;
/* Error reported by the Resource Manager (RM) to the Transaction Manager. */
uint rm_error;
} XID_STATE;
struct st_transactions {
XID_STATE xid_state;
}
在 commit 或 rollback 时,根据xid找到相应的事务,进行相应的操作
不充许DTP的嵌套,一个连接只能执行完一个DTP事务后,才充许执行下一下
除了加了一个全局标记XID之处,从任何方面看,都只是本地局部事务加了一层壳,
现在的MYSQL,
在DTP中,mysql需要应用程序充当AP和TM角色,没看到数据库服务器提供了TM功能
在DTP中,只看到了TM对RM的调用,没看到RM主动调用TM,相当于实现了XA接口的一半;
对于autocommit的实现也没看到,估计就是前后包装一层已实现的XA接口。