Release Notes for MongoDB 8.3

serverStatus Output

serverStatus includes the following new fields in its output:

• metrics.commands statistics for the connPoolStats command on mongod instances

• shardingStatistics.databaseCriticalSectionStatistics

• shardingStatistics.collectionCriticalSectionStatistics

• shardingStatistics.databaseVersionUpdateCounters

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.

findShardsOnConfigTimeoutMS Parameter

MongoDB 8.3 adds the findShardsOnConfigTimeoutMS parameter which sets the timeout in milliseconds for find operations against the config.shards namespace. For details, see findShardsOnConfigTimeoutMS.

config.csrs.indexes Removed

MongoDB 8.3 removes the config.csrs.indexes namespace.

Time Series

Starting in MongoDB 8.3, creating an index with the name of "_id_" or specifying a hint of "_id_" on time series collections returns an error.

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.

Fields to Track Use of Memory by Queries

Starting in MongoDB 8.3, you can use the following new fields to track query memory use:

Both fields appear in the following places:

• $currentOp (Aggregation Stage) output

• db.currentOp() output

• Database profiler output

• Log messages

• Slow query log messages

The peakTrackedMemBytes field also appears in the following places:

• Explain results

• PlanCache.list() output

• $planCacheStats output

cachePressureQueryPeriodMilliseconds Parameter

MongoDB 8.3 adds the cachePressureQueryPeriodMilliseconds parameter which sets the time interval MongoDB waits between checks for storage engine cache pressure. If the storage engine is under cache pressure, MongoDB aborts the oldest transaction. For details, see cachePressureQueryPeriodMilliseconds.

diagnosticDataCollectionDirectorySizeMB Parameter

MongoDB 8.3 increases the default value of diagnosticDataCollectionDirectorySizeMB from 200 to 500 MiB.

BSONObjectTooLarge Code for Upsert Errors

Starting in 8.3, upsert operations that produce a BSON object that is too large return the 10334 BSONObjectTooLarge error code. In earlier versions, upsert operations that produce a BSON object that is too large return the 17419 or 17420 error codes.

checkBSONConformance Field

Starting in 8.3, MongoDB no longer automatically enables the checkBSONConformance field in the db.collection.validate() method when full is true.