NoSQL -- three theoretical cornerstones of NoSQL -- cap -- Base -- final consistency

NoSQL Three theoretical cornerstones

NoSQL Three theoretical cornerstones ：CAP、BASE、 Final consistency

CAP

CAP Respectively ？

• C(Consistency) : Strong consistency . That is, multiple nodes have the same data at the same time .
• A(Availability) : Usability . Right or wrong , Anyway, the request must be responded .
• P(Tolerance of Network Partition) : Zone tolerance . Separate nodes can also run independently , That is, it is not limited to one machine .

Fish and bear paw , You can't have both.

The design concept of different products

BASE

mention NoSQL Of BASE characteristic , I have to say Transactions in traditional relational databases ACID Sexuality

ACID

ACID	meaning	Popular explanation
A	Atomicity Atomicity	All or nothing , All or nothing
C	Consistency Uniformity	When the transaction completes , All relevant data are consistent
I	Isolation Isolation,	Concurrent transactions are isolated from each other
D	Durability persistence	After the transaction completes , This effect is permanent

BASE

BASE	meaning	Popular explanation
B A	Basically Availble Basic available	Partition problem , The whole system is still available
S	Soft state Soft state	The data relative to the hard state is immediately consistent , Soft state tolerates data lag
E	Eventual consistency Final consistency	Here's an explanation

Final consistency

Strong consistency

• Strong consistency ： After an update , It can ensure that the subsequent access to the latest data

Weak consistency

• Weak consistency ： After an update , There is no guarantee that all the subsequent accesses are the latest data

Final consistency is a special case of weak consistency —— here “ There is no guarantee ”, But after a while , be “ Can guarantee ”; from “ final result ” see , Consistency is guaranteed .