MongoDB

What's new in this version:

Accessing Array Element Indexes in $map, $filter, and $reduce:
- MongoDB 8.3 improves access to array element indexes in $map, $filter, and $reduce aggregation expressions. You can use the new arrayIndexAs field to set a variable to store the index of an array element. You can also use the new $$IDX aggregation system variable to access the index of the current array element if you omit arrayIndexAs.

FTDC Statistics:
- Starting in MongoDB 8.3, Full Time Diagnostic Data Capture (FTDC) collects connPoolStats metrics for mongod processes
- serverStatus Output

serverStatus includes the following new fields in its output:
- aggregate.withExtension sub-field in metrics.commands.aggregate, tracking success and failure counts
- shardingStatistics.databaseCriticalSectionStatistics
- shardingStatistics.collectionCriticalSectionStatistics
- shardingStatistics.databaseVersionUpdateCounters
- metrics.ttl.deletedKeys
- metrics.ttl.durationMicros
- metrics.ttl.examinedDocuments
- metrics.ttl.examinedKeys
- metrics.extension
- metrics.extension.totalAggStageExecMicros
- metrics.extension.apiCallSuccesses
- metrics.extension.apiCallFailures
- metrics.extension.vectorSearch
- metrics.extension.vectorSearch.legacyVectorSearchUsed
- metrics.extension.vectorSearch.extensionVectorSearchUsed
- metrics.extension.vectorSearch.onViewKickbackRetries
- metrics.extension.vectorSearch.inSubpipelineKickbackRetries
- metrics.repl.network.oplogFetcherLagSeconds
- metrics.repl.network.oplogGetMoresProcessed
- queues.execution.admissions
- queues.execution.backgroundTasksDeprioritization
- queues.execution.deprioritizationGate
- queues.execution.heuristicDeprioritization
- queues.execution.heuristicDeprioritizationThreshold
- queues.execution.totalDeprioritizations
- queues.execution.usesPrioritization
- queues.execution.usesThroughputProbing
- queues.execution.nonDeprioritizable
- queues.execution.deprioritizable
- queues.execution.read.normalPriority.totalDelinquentAcquisitions
- queues.execution.read.normalPriority.totalAcquisitionDelinquencyMillis
- queues.execution.read.normalPriority.maxAcquisitionDelinquencyMillis
- queues.execution.read.lowPriority
- MongoDB 8.3 removes the service field in the serverStatus output
- Starting in MongoDB 8.3, you can exclude all optional fields from the serverStatus output by specifying none: 1. After you exclude all optional fields, you can then specify the fields you want to include.
- For details, see Exclude All Optional Fields
- You can also optionally specify lockContentionMetrics: 1 in the serverStatus command to include lockContentionMetrics in the output

String Conversion Enhancements:
- Starting in MongoDB 8.3, $toString can convert additional BSON types to strings, including objects, arrays, regular expressions, MaxKeys, MinKeys, and timestamps. For details, see $toString.
- MongoDB 8.3 introduces the optional base argument for $convert to convert between string and numeric values using bases 2, 8, 10, and 16. For details, see $convert.
- Array Conversion Enhancements
- Starting in MongoDB 8.3, you can convert strings that represent arrays using $convert or the shorthand expression $toArray
- You can also convert between binData and arrays of numeric values. For details, see Convert binData to Array and Convert an Array of Numeric Values to binData.

Object Conversion Enhancements:
- Starting in MongoDB 8.3, you can convert strings that represent objects using $convert or the shorthand expression $toObject

Geospatial Index Generation:
- Starting in MongoDB 8.3, if a document contains both GeoJSON and legacy numeric coordinate fields, geospatial index generation prioritizes GeoJSON coordinates.
- If your documents contain legacy numeric coordinate values that precede GeoJSON coordinates and existing indexes rely on that behavior, you might need to rebuild your geospatial indexes.
- This change may require you to rebuild geospatial indexes if your documents contain legacy numeric coordinate values that precede GeoJSON coordinates and existing indexes rely on that behavior. Review geospatial queries to confirm they return expected results.