innodb锁之间的兼容性判断

时间:2023-03-08 17:01:07
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));
}