Blocking type of gbase 8s concurrency control

         Follow the lock Patterns of behavior , Can be 8s The middle lock is divided into ： Shared lock 、 Exclusive lock 、 Lifting lock Three types of .

Shared lock [ Read the lock 、S lock ]

         Shared lock , It can prevent other users from modifying records . But you can share locks on the data object at the same time & Intent locks . Only after the data is released from all shared locks , Before you can lock it up .

         Apply realistic examples ： There are many teachers' blackboard writing on the blackboard in the classroom , Each student takes notes while reading , No one wants a troublemaker to alter on the blackboard , This will cause the things in the past to be messy . So when everyone is looking at the blackboard , Everyone declares that no one is allowed to change now 【 Write lock 】. But you can tell us in advance what you want to change 【 Intent locks 】, But if you want to read blackboard , Then you have to join us 【 Shared lock 】.

Exclusive lock [ Write lock 、X lock ]

         Exclusive lock , Used to manage and update , It can also be called exclusive lock , Be on X Lock data , Only lock transactions are allowed to read and write to them .

Lifting lock [ Intent locks 、U lock ]

         Indicates that the transaction has the intention to modify the record , It is a transitional type of lock , Will be U lock Up to the X lock , If some data has U lock , Only other data can be on this transaction S lock .

summary ： Write locks do not coexist with any locks 、 Read lock can coexist with read lock , There can only be one Lifting lock .

ps： I don't know the word lock after writing these introductions of lock .