我在myql 8.0.11上的“显示引擎innodb状态”中的死锁下方找到了。
根据我的理解，两个查询应仅锁定一行（主键user_id随两个查询而不同）。但是第二个查询"*** (2) HOLDS THE LOCK(S): "RECORD LOCKS space id 5461 page no 76054 n bits 96 index PRIMARY of table user“`
，并且第一个查询正在等待获取相同的锁。我不明白为什么？即使两个锁语句都说"locks rec but not gap"，这意味着两个锁都只锁定单个记录（应该是它们的主键user_id）
想知道我的理解（如上所述）是正确的吗？如果是，那么如何解释以下日志？
*** (1) TRANSACTION:
mysql tables in use 1, locked 1
LOCK WAIT 3 lock struct(s), heap size 1136, 2 row lock(s), undo log entries 1
update `user` set `user`.`xxxx` = 1 where ( user_id = 4939334)
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 5461 page no 76054 n bits 96 index PRIMARY of table `user` trx id 5385693398 lock_mode X locks rec but not gap waiting
Record lock, heap no 24 PHYSICAL RECORD: n_fields 20; compact format; info bits 0
*** (2) TRANSACTION:
mysql tables in use 1, locked 1
3 lock struct(s), heap size 1136, 2 row lock(s), undo log entries 1
update `user` set `user`.`xxxx` = 1 where ( user_id = 4917613)
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 5461 page no 76054 n bits 96 index PRIMARY of table `user` trx id 5385693399 lock_mode X locks rec but not gap
Record lock, heap no 24 PHYSICAL RECORD: n_fields 20; compact format; info bits 0
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 5461 page no 63136 n bits 88 index PRIMARY of table `user` trx id 5385693399 lock_mode X locks rec but not gap waiting
Record lock, heap no 19 PHYSICAL RECORD: n_fields 20; compact format; info bits 0