Intention lock

Intent locks （Intention Lock）, also called I lock . For table lock .
When a transaction adds a shared lock or exclusive lock to the data row of the table , At the same time, an identifier will be set for the table , It means that there is already a row lock , When other transactions want to lock the table , There is no need to judge row by row whether row locks may conflict with table locks , Directly reading this sign can determine whether you should lock your watch . Especially when there are many records in the table , It is inefficient to judge the way of adding table lock row by row . And this sign is the intention lock .

• Intention sharing lock ,IS lock , Before applying a shared lock to the entire table , You need to obtain the intention sharing lock first .
• Intention exclusive lock ,IX lock , Before locking the whole watch , You need to get the intention exclusive lock first .

Mainly to improve the efficiency of adding meter lock .

Lock mode ：
Cannot create... Manually .

---

Table level read lock ：
lock table user_info read;
Table level write lock ：
lock table user_info write;