1 innodb lock
1.1 s lock, i.e. read lock, i.e. share lock
1.2 x locks, i.e. write locks, exclusive locks
1.3 The relationship between s lock and x lock
Multiple read locks can coexist, but read locks cannot coexist with write locks. Write locks and write locks cannot coexist.
1.4 Gap lock
It is to lock a piece of data, such as the row with id greater than 3 and less than 10, to prevent data with id=4 from being inserted.
2 innodb high concurrency
It is suitable for high concurrency with more reads and fewer writes, so in order to obtain high concurrency, read and write separation is necessary.
3 deadlock
Transaction A has 1 and needs 2, and transaction B has 2 and needs 1.
4 Three kinds of row locks of innodb
First, record lock
A lock on a single row.
Second, gap lock
Locks on gaps, excluding the row itself, resolve phantom reads.
Third, next lock
Including the gap and the line itself.