innodb锁之间的兼容性判断

检查锁与锁之间的兼容性

路径：/mysql-5.5.43/storage/innobase/lock/lock0lock.c 

实现：见锁的强度比较

 

 row 可理解为 lock 的锁模式

 column 可理解为 预加锁的模式

反过来也行

 

速记：只要包括X字符，跟谁都不兼容

 

/* LOCK COMPATIBILITY MATRIX * IS IX S X AI * IS + + + - + * IX + + - - + * S + - + - - * X - - - - - * AI + + - - - * * Note that for rows, InnoDB only acquires S or X locks. * For tables, InnoDB normally acquires IS or IX locks. * S or X table locks are only acquired for LOCK TABLES. * Auto-increment (AI) locks are needed because of * statement-level MySQL binlog. * See also lock_mode_compatible(). */

/*********************************************************************//** Calculates if lock mode 1 is compatible with lock mode 2. @return nonzero if mode1 compatible with mode2 */ UNIV_INLINE ulint lock_mode_compatible( /*=================*/
    enum lock_mode    mode1,    /*!< in: lock mode */
    enum lock_mode    mode2)    /*!< in: lock mode */ { ut_ad(mode1 == LOCK_X || mode1 == LOCK_S || mode1 == LOCK_IX || mode1 == LOCK_IS || mode1 == LOCK_AUTO_INC); ut_ad(mode2 == LOCK_X || mode2 == LOCK_S || mode2 == LOCK_IX || mode2 == LOCK_IS || mode2 == LOCK_AUTO_INC); return((LOCK_MODE_COMPATIBILITY) & LK(mode1, mode2)); }