MongoDB 4.4.0-rc0, the first release candidate of MongoDB 4.4, is out and is ready for testing. This is the culmination of the 4.3.x development series, and includes many exciting new features. Please review the release notes for more about what’s new, upgrade procedures, and how to report an issue. Here are some of the highlights:
MongoDB Query Language
- Union: Enhancing the power of the MongoDB Query Language, you can now combine results from multiple collections into a single result set in the database, allowing your users to easily blend data from multiple sources for deeper exploration and analysis.
- New aggregation expressions: simplifying your code, it’s now easier to search and manipulate strings and evaluate the first and last elements of an array. To simplify schema analysis and performance optimization, you can use new binary expressions to return the size of binary objects in your documents
Scale-Out Flexibility & Performance
- Refinable shard keys: With the ability to define and refine your shard keys at any time, you can now adapt data distribution across your cluster as your database grows and applications evolve, without impacting system availability.
- Compound hashed shard keys: By adding support for hashing any single field in a compound shard key, you get higher database throughput by more evenly distributing load across shards, without losing data locality or creating hot shards as your applications scale.
- Hedged Reads: High latency directly correlates to lost revenue. To minimize p95 and p99 latencies, the MongoDB query router is configured by default to submit read requests with read preference “nearest” to multiple replicas in a sharded cluster, returning results to the client as soon as the quickest node responds.
Resilience and Security
- Mirrored Reads: Reducing the user impact of replica set elections during planned maintenance, you can pre-warm the caches of secondaries by mirroring a percentage of reads to them in advance of stepping down the primary.
- Resumable Initial Sync: The initial sync process now automatically resumes after encountering transient network errors, making it easier and faster to scale-out by adding new replicas to your cluster or recover nodes that have fallen too far behind other members
– The MongoDB Team