rec锁(Record Lock):记录锁,直接锁定数据记录本身。当一个事务对某条记录加上了rec锁,其他事务就不能对这条记录进行更新或删除操作,直到该锁被释放。 gap锁(Gap Lock):间隙锁,锁定一个范围,但不包括记录本身。gap锁主要用于防止幻读(Phantom Reads),即当一个事务读取一个范围内的记录时,另一个事务在这个范围...
X,GAP,INSERT_INTENTION→ right to insert a new row into the gap before this row. Despite “X” in its name it is actually compatible with others threads trying to insert at the same time. (插入检查唯一约束会使用这个锁, 但是只要不违反唯一约束, 每个线程都可以获取这个锁. 但是和上面的S,GAP...
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开销小,加锁快;不会出现死锁;锁定粒度大,发生锁冲突的概率最高,并发度最低。 1. 行级锁和间隙锁 Record lock:记录锁 Gap lock:间隙锁,锁定一个范围,但不锁定记录本身 Next-Key lock:锁定范围和记录本身 在RR级别解决幻读问题 唯一索引退化为行锁,不可能插入相同的数据 普通索引退化为间隙锁 非索引字段会给...
lock_mode x locks rec but not gap waiting 这个信息通常出现在数据库系统中,特别是在使用像MySQL这样的关系型数据库时。这个信息描述了锁的行为,特别是行锁(record lock)和间隙锁(gap lock)的区别。 基础概念 行锁(Record Lock):锁定索引记录本身,防止其他事务修改这条记录。 间隙锁(Gap Lock):锁定索...
GAP", "X", "X,GAP", "IS", "IS,GAP", "IX", "IX,GAP", "AUTO_INC", and "UNKNOWN". There are no other permitted values. but actually, there are other permitted values: "S,REC_NOT_GAP", "X,REC_NOT_GAP". and readers can not under stand what "S", "S,GAP" means, which...
update-wait-lock-mode-x-locks-rec-but-not-gap-vs-update-wait-lock-mode-s-holds-lock-mode-x-locks-rec-but-not-gap === ## 死锁特征 1. update WAITING FOR lock_mode X locks rec but not gap 2. update WAITING FOR lock mode S, HOLDS lock_mode X locks rec but not gap ## 死锁日志...
但是“mixed-mode inserts”这种插入下就和traditional方式有区别了,这种模式下可能用户会精确提供部分自增列的行数,但是不是所有的都会明确知道,这个时候,innodb会分配比已知要插入的行数更大的自增值给后面的insert,这样分配的值也是连续的,但是可能就和前面的自增值有gap了,这个时候gap value会lost。
gap locks explanation, but there we can read: "A type of gap lock called an insertion intention gap lock is set by INSERT operations prior to row insertion. This lock signals the intent to insert in such a way that multiple transactions inserting into the same index gap need not wait for...
记录锁(LOCK RECNOT GAP): lock mode X locks rec but not gap 间隙锁(LOCK GAP): lock mode X locks gap before rec Next-key 锁(LOCKORNIDARY): lock mode X 插入意向锁(LOCK INSERT INTENTION): lock_mode X locks gap before rec insert intention ...