Version 4.0
(1) Cross-document transaction support (ACID)
The first support NoSQL cloud database transactions across documents, document model speed, flexibility and functionality combined with ACID guarantee. Now, using MongoDB to solve a variety of use cases easier.
(The presence of 4.0 maximum transaction modified 16MB, transaction execution time limit is not too long)
(2) 40% faster migration
Concurrent reading and writing, so that the new fragment shard transport properties improved about 40%, faster new node bearer service pressure.
(3) read performance greatly expanded
4.0 by means of transaction characteristics, so that the standby node is not blocked because the synchronization log read request.
(4) Change Stream enhancement
Before MongoDB3.6, if we want to change data in MongoDB database listens, usually by "listening and playback oplog". From the beginning MongoDB3.6 supported Change Streams break this impasse. Change Streams enables variable data monitor easy to use. If you only need to listen for a change in a collection, MongoDB3.6 to meet your needs. In version 4.0, we can for the entire database or a number of instances (the replication set or sharding) fluctuates monitor. And watch()one collection of different, we may be 4.0 watch()of a database, or instance.
Version 4.2
(1) Distributed Transaction
4.2 supports distributed transactions, MongoDB by way of two-phase commit protocol to achieve modifications that occur across multiple Shard, either simultaneously or not take place, ensure ACID properties of transactions.
In use, the distributed transactions 4.2 4.0 replica set with the transaction using exactly the same way, users do not care about how the back-end data distribution.
(2) high availability
In 4.0 provides Retryable Write function in the new version 4.2, MongoDB adds Retryable Read function, for some temporary network problems, users do not need to achieve their own retry logic, MongoDB will automatically retry processing, to ensure the continuity of business users.
(3) Index enhanced with Wildcard Index type
MongoDB 4.2 introduced Wildcard Index, can be automatically indexed for a range of fields, to meet the needs of rich query.
(4) field level encryption
In addition to MongoDB supports SSL, TDE and other security mechanisms, at 4.2 introduces support for "field-level encryption", to achieve the user Value JSON documents are automatically encrypted. The whole process is completed in the Driver layer, transmission, storage to the server documentation Value is the ciphertext, MongoDB 4.2 Drvier supports various encryption policy, you can turn on encryption for the collection, field dimensions, the encryption process is completely transparent to developers.
Reprinted from: https: //www.cnblogs.com/xuliuzai/p/10435793.html