What Is New in MongoDB 2.8
MongoDB 2.8 is a major release focused on concurrency, security, and operational enhancements. The key improvements are summarized in the table below.
| Category | Key Changes |
|---|---|
| Concurrency | Document-Level Locking for WiredTiger storage engine |
| Security | Encrypted Storage Engine, LDAP Authorization, Auditing |
| Aggregation | New operators: $ceil, $floor, $ln, $log10, $sqrt |
| Indexing | Partial Indexes |
| Replication | Initial Sync Improvements |
| Deprecations | MMAPv1 storage engine deprecated |
How does document-level locking improve performance?
The WiredTiger storage engine introduces document-level concurrency control, a massive leap from the previous collection-level locking. This allows multiple operations to modify different documents within the same collection simultaneously. In practice, this drastically increases write throughput and reduces contention for heavily used collections.
What security features were added?
MongoDB 2.8 rolled out a comprehensive security suite. The encrypted storage engine protects data at rest, transparently encrypting everything from journals to indexes. Auditing provides a detailed log of system activity for tracking changes. LDAP authorization allows user roles and privileges to be managed directly through an external LDAP server, simplifying user management in enterprise environments.
What are the new aggregation framework operators?
The aggregation framework got a boost with new arithmetic expression operators. You can now perform calculations like $ceil, $floor, $ln (natural log), $log10, and $sqrt directly within your aggregation pipelines. This saves you from having to process basic mathematical operations outside of the database.
When should I use partial indexes?
Partial indexes are a smart way to reduce index size and improve performance. You create an index that only includes documents that meet a specified filter expression. This is perfect for indexing a frequently queried subset of data, like all active users, without the overhead of indexing the entire collection.
FAQ
Is the WiredTiger engine production-ready in 2.8?
Yes, WiredTiger is designated as the production-ready storage engine starting with MongoDB 2.8. Its document-level locking and compression features make it the recommended choice for most new deployments over the older MMAPv1 engine.
Does the encrypted storage engine impact performance?
There is a performance overhead associated with encryption and decryption, but it is generally considered acceptable for the security benefit. The engine uses AES256 cipher blocks and native OS encryption features for the implementation.
Can I use LDAP for authentication and authorization?
In 2.8, LDAP support is specifically for authorization, meaning it manages user roles and privileges. Authentication (verifying user credentials) still needs to be handled internally by MongoDB or through a different external mechanism.
What happens to my existing MMAPv1 databases?
They continue to work, but MMAPv1 is deprecated. You can migrate data from MMAPv1 to WiredTiger using mongodump and mongorestore. This migration is a great opportunity to benefit from the new concurrency model.
Are partial indexes sparse indexes?
They are related but more powerful. A sparse index only indexes documents that contain the field, even if it's null. A partial index uses a filter expression, so you can index documents based on any condition, not just the existence of a field.