The document presents an overview of the new features and enhancements in MongoDB 8.0, which includes significant performance improvements in write and read operations, workload-specific optimizations, and advanced sharding capabilities. It also discusses command path optimization, improved query insights, and the introduction of persistent query settings to enhance operational efficiency. Additionally, it highlights the expected performance boosts for various workloads, including time series data management and queryable encryption improvements.

1. Manosh Malai
CTO, Mydbops LLP
Mydbops MyWebinar Edition 34
What’s New In
MongoDB 8.0

2. About Me
Manosh Malai
❏ Interested in Open Source technologies
❏ Interested in MongoDB, DevOps & DevOpSec Practices
❏ Tech Speaker/Blogger
❏ MongoDB User Group Leader(Bangalore)

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4. ❏ Performance Enhancements
❏ Workload Specific Improvements
❏ Time Series Enhancements
❏ Command Path Optimization
❏ Express Path Efficiency
❏ Advanced Sharding Capabilities
❏ Moving unsharded collections
❏ Converting sharded collections to unsharded
❏ Queryable Encryption Enhancements
❏ Persistent Query Settings
Agenda

5. Performance
Enhancements

6. ❏ Up to 54% improvement in write performance (YCSB Write Bulk Data)
❏ Read performance gains of up to 27% (YCSB Read-Heavy workloads)
❏ Mixed workload improvements (95% Read, 5% Write) see up to 25% gains
❏ Linkbench benchmarks suggest an 18% performance increase
❏ Time Series workloads (TSBS) benefit from up to a 60% boost
Performance Enhancements
Benchmark Improvement
YCSB Write-Heavy (100% Write) Up to 54%
YCSB Read-Heavy (95% Read) Up to 27%
Linkbench (if data available) Up to 18%
Time Series Workloads (TSBS) Up to 60%

7. Workload Specific
Improvements

8. MongoDB 5.0, 6.0 & 7.0
❏ Storage Engine: Classic —> SBE
❏ Significant improvements: $group, $project, $match, $sort, $lookup(in replica) Operation
❏ Columnar Storage: Boosts performance for aggregation, sorting, visualization(Time Series Enhancements)
❏ Game-Changer: Efficiently handles large volumes of time series data
MongoDB 8.0 (Expected)
❏ Block Processing: Faster queries $group 60% Improvement
❏ Awaiting Details: Confirmed improvements, documentation pending
Workload Specific Improvements

9. Command Path Optimization in MongoDB 8.0
❏ Overview: Major overhaul of the internal command path handling
❏ Performance: Significant enhancements for faster response times
❏ Efficiency: More efficient database operations guaranteed
References
➔ https://jira.mongodb.org/browse/SERVER-80296
➔ https://jira.mongodb.org/browse/SERVER-84283
➔ https://jira.mongodb.org/browse/SERVER-82831
Workload Specific Improvements

10. Express Path Latency Improvement
❏ Improvement: 17% Latency Reduction
❏ Key Enhancement: Introduction of SortedDataKeyValueView and seekForKeyValueView
Current Method
❏ Invocation: Uses SortedDataInterface::seek with index key
❏ Creation: Constructs underutilized BSONObj
❏ Data Retrieval: Fetches IndexKeyEntry with RecordId
Reference:
→ https://jira.mongodb.org/browse/SERVER-89445
→ mongo-r8.0.0-rc10/src/mongo/db/storage/key_string.h
→ mongo-r8.0.0-rc10/src/mongo/db/storage/sorted_data_interface.h
Express Path Efficiency

11. Express Path Latency Improvement
Proposed Method
❏ Direct Retrieval: Uses seekForKeyValueView
❏ Avoids BSONObj: Bypasses unnecessary BSONObj creation
❏ Efficient Data Access: Combines keystring and RecordId into a tuple
Benefits
❏ Reduced Overhead: Streamlines query process
❏ Enhanced Speed: Faster query execution in the Express Path
❏ Resource Efficiency: Better performance and resource allocation
Express Path Efficiency

12. ❏ Google TCMalloc
❏ Per-CPU Cache: Faster data access and reduced latency.
❏ 18% Memory Fragmentation Reduction: More efficient use of memory.
❏ Enhanced Peak Load Performance: Better responsiveness and stability under high load.
Reduced Memory Fragmentation

13. Query Insight Features
❏ Detailed Namespace-Level Metrics: Fast issue resolution with performance comparison across
collections.
❏ Heatmap Panel: Visualize and understand query trends.
Improved Visibility In Query Insights: MongoDB Atlas

14. Query Shape and Rejection Filters
Query Shape Standardization:
❏ Uses kToRepresentativeParseableValue method to create a unified query shape.
❏ Focuses on structural patterns for optimization.
Reject Operations Using Query Shape:
❏ Query Shape and Operation Rejection:
❏ Standardizes query structure for optimization.
❏ Identifies and simplifies structurally similar queries.
❏ Rejects resource-consuming queries via their query shape.
Improved Visibility In Query Insights: MongoDB Atlas
db.adminCommand({
setQuerySetting: ‘xxxxxx’,
Settings: {
Reject: true
}
})

15. Challenges with Previous Methods
❏ Using planCacheSetFilter
❏ Configuration not persisted across restarts.
❏ Operational challenges in maintaining settings.
Code example:
Persistent Query Settings
db.runCommand(
{
planCacheSetFilter: <collection>,
query: <query>,
sort: <sort>,
projection: <projection>,
indexes: [ <index1>, <index2>, ...],
}
)

16. New Feature: Persistent Query Settings
Advantages:
❏ Applies index for specific query shapes matching hash.
❏ Replicates settings across replica set members.
❏ Persists configurations between restarts.
❏ No application code changes required.
Persistent Query Settings
db.adminCommand({
setQuerySettings: '<QueryShapeHash>',
indexFilters: '<Index Name>'
})
{
planSummary: "COLLSCAN",
queryShapeHash: '7F312F79FCOC3_*',
durationMilli s: 11123232 // Too long
}
Code Example slow query log entry:

17. Global Read Timeout Definition
❏ Set a default timeout (maxTimeMS) for all read operations across your cluster.
❏ Protects against resource-intensive queries.
❏ Ensures efficient query execution and cluster stability.
Code example:
Define Read Timeout Globally
db.adminCommans(
{
setClusterParameter: {
defaultMaxTimeMS: { readOperations: 20000}
}
}
}

18. Move Unsharded Collection
Simplified Process
❏ Use db.adminCommand({moveCollection: "mydbops.mongodb", toShard: "shard1"}) to relocate unsharded
collections.
❏ Ensures seamless transfer without disrupting operations.
Convert Sharded Collection to Unsharded
Streamlined Operation
❏ Utilize db.adminCommand({unshardCollection: "mydbops.mongodb", toShard: "shard1"}) for converting
sharded collections to unsharded.
❏ Enables faster resharding, reducing impact on workload significantly.
Advanced Sharding Capabilities

19. Example:
Resharding 500GB in a 1TB cluster now completes in hours, enhancing scalability and operational
efficiency.
Advanced Sharding Capabilities

20. Range Query Support
Enhanced Functionality:
❏ Introduces support for range queries within date ranges and numeric bounds.
❏ Includes Decimal 128 for accurate handling of financial values.
❏ Encrypted fields now support operators like $gt, $lt, $gte, and $lte.
Queryable Encryption Enhancements in MongoDB 8.0

21. Thank you!