MongoDB 4.0 has been
released on Aug 6, 2018, with tremendous new features specially ACID
transactions.
I have
listed the MongoDB 4.0 new features below
Read concern snapshot
- MongoDB 4.0
introduces a new concern level snapshot for the multi-document transactions.
- Read concern
helps in targeting consistency and isolation properties of data
- This new feature
ensures that a consistent view of data is returned to the client,
whether data is being modified simultaneously
Data Type Conversions
- This is new
in MongoDB 4.0 to
convert data types, this comes under the aggregation framework and can be used with the help of the $convert expression
New String Operators
Below are
the string operators added in the new version 4.0
- $ltrim : Removes
white spaces or specified characters from beginning of string
- $rtrim : Removes white spaces or specified characters from end of
the string
- $trim : Removes white spaces or specified
characters from beginning and end of the string
Read Preference
- In the previous release MongoDB blocked
secondary reads while oplog entries were applied.
- Now there is
improved read latency and increased throughput from the replica set which
helps in maintaining a consistent ordering of data
Sharding Operations and
Migration throughput
- Sharded migrations are now up 40% faster
helping for better distribution of data
- Operations can list and kill queries running in shared
cluster.
Locking System
- By default, multi-document transactions wait 5
milliseconds to acquire locks required by operations in transactions
- If transactions can not acquire their required locks
within 5 milliseconds the transactions abort
The latest Minor release is
4.0.5 (Dec 20, 2018)
Below
will be featured in the upcoming MongoDB 4.2
- Removed MMAPv1 storage engine
- Removed a few commands and methods like group, eval,
copydb etc.
- Security improvements like adding TLS and depreciating
SSL
- Aggregation improvements
- Transaction Manager
[Also
read: Introduction to MongoDB MongoDB storage Engines]
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