Several important theories of the NoSQL world

As with everything, the rise of NoSQL is premised on a number of theoretical supports, which are supported by the following theories, and the direction of NoSQL can be so clear.

1.CAP theory

The CAP theory is undoubtedly the most important cause of the change in technology trends from relational database systems to NoSQL systems.

The CAP (consistency,availability,patition tolerance) theory states that in any distributed system, it is possible to satisfy only the two of the three that are consistent, usable, and tolerant of partitioning. So don't take the time to focus on how to meet all three of them.

The proof of the principle is simply that, in the case of ensuring partition tolerance, consistency and availability are not achievable at the same time, high consistency sacrifices availability, and high availability compromises consistency. (Why do you want to ensure partition tolerance?) Data partitioning is a basic requirement for today's increasingly large network applications.

Proof process: Brewer ' s CAP theorem

2. consistent hash

This needless to say, the person who used MC should be clear, direct:

3.MapReduce

The MapReduce idea is divided into map and reduce two parts, in a nutshell, map is to divide the large amount of computation, in order to calculate in parallel, reduce is to combine the results of parallel computation in order to get a final output.

See Wikipedia:mapreduce for a more detailed description.

Google documentation for MapReduce PDF version: mapreduce:simplified Data processing on Large Clusters

4.Gossip

Gossip is a theory applied to peers (not the current popular gossip girl[Gossip Girl), whose main process is to communicate with all other N-1 nodes through each node in an N-node cluster to synchronize data. Gossip is based on the requirement that a master exists in the cluster and that the change of one node can be communicated to all other nodes in a virus-transmitted manner, and that the system increases or decreases the cost of a junction by almost 0.

More detailed description See WIKIPEDIA:GOSSIP

And more ...

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Several important theories of the NoSQL world