Versions

This section describes the compatibility between DDS versions and MongoDB, aggregation operation compatibility, and DDS features of different versions.

MongoDB-Compatible Features

**Table 1** MongoDB-compatible features
Category	Details	DDS 4.0	DDS 4.2	DDS 4.4	Community Edition MongoDB 4.2	Community Edition MongoDB 4.4
Database commands	The find command supports the allowDiskUse field, which allows MongoDB to use temporary files on disk to store data exceeding the system memory limit while processing a non-index sort operation.	×	×	√	×	√
Database commands	New syntax and usage of projection. In projection, syntax of aggregation functions is supported, for example, using aggregation operators. In projection, data is encoded in JSON format and nested to map specified fields. In projection, the $ character can be used to specify a specific index subelement for a mapped array element.	×	×	√	×	×
Distributed transactions	Distributed transactions are supported. Distributed transactions refer to multi-document transactions on sharded clusters and replica sets. Multi-document transactions (whether on sharded clusters or replica sets) are also known as distributed transactions starting in MongoDB 4.2.	×	√	√	√	√
	The 16 MB total size limit for a transaction was removed.	×	×	√	√	√
	The MongoDB drivers must be updated for MongoDB 4.2.	×	√	√	√	√
Aggregation	The aggregation capability is improved. Data can be updated in the aggregation pipeline. Added $merge. Added $accumulator and $function. Supported union All. Added $unionWith. For details about aggregation operations, see Table 2.	√	√	√	√	√
Wildcard indexes	Wildcard indexes are supported.	√	√	√	√	√
Sharded cluster	A document's shard key field value can be changed.	×	×	√	√	√
	The fields associated with the shard key can be adjusted.	√	√	√	×	√
	Collections can be sharded using a composite shard key that consists of a single hash field.	×	×	√	×	√
	The 512-byte size limit on a shard key was removed.	×	√	√	×	√
	Multi-document transactions allow the creation of indexes and collections (non-distributed transactions).	×	×	×	×	√
Indexes	The size limit on indexes was removed.	√	√	√	√	√
	The length limit on index names was removed.	√	√	√	√	√
	Composite indexes can contain hash indexes.	×	×	√	×	√
	Hidden indexes are supported for commissioning.	√	√	√	×	√
	The size limit on collection namespaces is changed. The length of <database>.<collection> is increased from 120 bytes to 255 bytes.	√	√	√	√	√
Other optimized features	Default Read and Write Concern Global default read/write concerns, involving connection and command read/write contexts.	×	×	√	×	×
	Jumbo chunks can be migrated.	×	×	√	×	×
	Hedge query is supported.	×	×	√	×	×
	The dds mongos node supports JavaScripts to support some special aggregation operators.	×	×	√	×	×

√ indicates that an item is supported, and × indicates that an item is not supported.
For details about how to evaluate the compatibility when migrating MongoDB from a later version to an earlier version, see How Do I Evaluate the Compatibility When Migrating MongoDB from a Later Version to an Earlier Version?

Aggregation Operations

**Table 2** Aggregation operations
Operator	DDS 4.0	DDS 4.2	DDS 4.4	MongoDB 4.2 Community Edition	MongoDB 4.4 Community Edition
$sin	√	√	√	√	√
$cos	√	√	√	√	√
$tan	√	√	√	√	√
$asin	√	√	√	√	√
$acos	√	√	√	√	√
$atan	√	√	√	√	√
$atan2	√	√	√	√	√
$asinh	√	√	√	√	√
$acosh	√	√	√	√	√
$atanh	√	√	√	√	√
$degreesToRadians	√	√	√	√	√
$radiansToDegrees	√	√	√	√	√
$round	√	√	√	√	√
$trunc	√	√	√	√	√
$regexFind	√	√	√	√	√
$regexFindAll	√	√	√	√	√
$regexMatch	√	√	√	√	√
$merge	√	√	√	√	√
$planCacheStats	×	×	×	√	√
$replaceWith	√	√	√	√	√
$set	√	√	√	√	√
$unset	√	√	√	√	√
NOW	√	√	√	√	√
CLUSTER_TIME	√	√	√	√	√
findAndModify	√	√	√	×	√
update	√	√	√	√	√
$accumulator	√	√	√	×	√
$binarySize	√	√	√	×	√
$bsonSize	√	√	√	×	√
$first	√	√	√	×	√
$function	√	√	√	×	√
$last	√	√	√	×	√
$isNumber	√	√	√	×	√
$replaceOne	√	√	√	×	√
$unionWith	√	√	√	×	√

√ indicates that an item is supported, and × indicates that an item is not supported.
For details about how to evaluate the compatibility when migrating MongoDB from a later version to an earlier version, see How Do I Evaluate the Compatibility When Migrating MongoDB from a Later Version to an Earlier Version?

DDS Features

**Table 3** DDS features
Category	Feature	Constraint	DDS 4.0			DDS 4.2			DDS 4.4			Remarks
DB Instance Type			Single Node	Replica Set	Cluster	Single Node	Replica Set	Cluster	Single Node	Replica Set	Cluster	-
Instance Management	Creating an instance	-	√	√	√	√	√	√	√	√	√	-
	Deleting an instance	-	√	√	√	√	√	√	√	√	√	-
	Restarting an instance	-	√	√	√	√	√	√	√	√	√	-
	Resetting a password	-	√	√	√	√	√	√	√	√	√	-
	Changing an instance name	-	√	√	√	√	√	√	√	√	√	-
	Changing an instance port	-	√	√	√	√	√	√	√	√	√	-
	Performing a switchover	-	√	√	√	√	√	√	×	√	×	-
	Exporting the instance list	-	√	√	√	√	√	√	√	√	√	-
	Compute scale-up	-	√	√	√	√	√	√	√	√	√	-
	Compute scale-down	-	√	√	√	√	√	√	√	√	√	-
	Adding nodes	-	-	√	√	-	√	√	√	√	√	-
	Deleting nodes	-	-	×	×	-	×	×	×	×	×	-
	Storage scale-up	-	√	√	√	√	√	√	√	√	√	-
	Storage scale-down	-	×	×	×	×	×	×	×	×	×	-
	Restarting a node	-	√	√	√	√	√	√	√	√	√	-
	OpenAPI	-	√	√	√	√	√	√	√	√	√	-
	SDK	-	√	√	√	√	√	√	√	√	√	-
	Task center	-	√	√	√	√	√	√	√	√	√	-
	Tags	-	√	√	√	√	√	√	√	√	√	-
	Quotas	-	√	√	√	√	√	√	√	√	√	-
Network Management	EIP-based public network access	-	√	√	√	√	√	√	√	√	√	-
	Changing a private IP address	-	√	√	√	√	√	√	√	√	√	-
	Cross-CIDR access	-	√	√	√	×	×	×	√	√	√	In DDS 4.2 and 4.4, the client and an instance can communicate only when they are in the same VPC and subnet. If the client is a container, the client can communicate with an instance using an IP address in the default CIDR block 192.168.0.0/16, 172.16.0.0/24, or 10.0.0.0/8.
	Changing an AZ	-	√	√	√	×	×	×	√	√	√	In DDS 4.2 and 4.4, deploying an instance across multiple AZs is recommended.
	Domain name access	-	√	√	√	×	×	×	×	×	×	In DDS 4.2 and 4.4, you are advised to use the IP address to access an instance.
Security	Security group	-	√	√	√	√	√	√	√	√	√	-
	SSL	-	√	√	√	√	√	√	√	√	√	-
	Instance recycle bin	-	√	√	√	√	√	√	√	√	√	-
	Storage encryption	-	√	√	√	×	×	×	×	×	×	-
Billing	Converting a single node to a replica set	-	×	-	-	×	-	-	×	-	-	-
	Pay-per-use	-	√	√	√	√	√	√	√	√	√	-
	Yearly/Monthly	-	√	√	√	√	√	√	×	×	×	-
	Changing pay-per-use to yearly/monthly	-	√	√	√	√	√	√	×	×	×	-
	Changing yearly/monthly to pay-per-use	-	√	√	√	√	√	√	×	×	×	-
Versions	Minor version upgrade (manual)	-	√	√	√	√	√	√	√	√	√	-
	Minor version upgrade (automatic)	-	×	×	×	×	×	×	×	×	×	-
	Major version upgrade (manual)	-	×	×	×	×	×	×	×	×	×	-
Logs	Viewing slow query logs	-	√	√	√	√	√	√	√	√	√	-
	Downloading slow query logs	-	√	√	√	√	√	√	√	√	√	-
	Masking slow query logs	-	√	√	√	√	√	√	√	√	√	-
	Querying error logs	-	√	√	√	√	√	√	√	√	√	-
	Downloading error logs	-	√	√	√	√	√	√	√	√	√	-
	Configuring the audit log policy	-	√	√	√	√	√	√	√	√	√	-
	Querying audit logs	-	√	√	√	√	√	√	√	√	√	-
	Downloading audit logs	-	√	√	√	√	√	√	√	√	√	-
Parameters	Changing a parameter template	-	√	√	√	√	√	√	√	√	√	-
	Creating a parameter template	-	√	√	√	√	√	√	√	√	√	-
	Deleting a parameter template	-	√	√	√	√	√	√	√	√	√	-
	Modifying a parameter template	-	√	√	√	√	√	√	√	√	√	-
	Comparing parameter templates	-	√	√	√	√	√	√	√	√	√	-
Backup and Restoration	Automated backup	-	√	√	√	√	√	√	√	√	√	-
	Manual backup	-	√	√	√	√	√	√	√	√	√	-
	Deleting a backup	-	√	√	√	√	√	√	√	√	√	-
	Restoring to a new DB instance	-	√	√	√	√	√	√	√	√	√	-
	Restoring data to the original DB instance	-	√	√	√	√	√	√	√	√	√	-
	Restoring to an existing DB instance	-	×	×	×	×	×	×	×	×	×	-
	Configuring an automated backup policy	-	√	√	√	√	√	√	√	√	√	-
	Incremental backup	-	√	√	√	×	×	×	×	×	×	-
	PITR	-	×	√	×	×	×	×	×	×	×	-
	Downloading a full backup file	-	√	√	√	√	√	√	√	√	√	-
	Downloading an incremental backup file	-	-	-	-	-	-	-	-	-	-	-
	Cross-region backup	-	√	√	√	√	√	√	√	√	√	-
	Cross-region restoration	-	√	√	√	√	√	√	√	√	√	-
O&M	Creating a database role	This operation can only be performed by calling a specified API.	√	√	√	√	√	√	√	√	√	-
	Creating a database account	This operation can only be performed by calling a specified API.	√	√	√	√	√	√	√	√	√	-
	Deleting a database role	This operation can only be performed by calling a specified API.	√	√	√	√	√	√	√	√	√	-
	Dropping a database user	This operation can only be performed by calling a specified API.	√	√	√	√	√	√	√	√	√	-
	Monitoring by seconds	Minimum interval: 5s	√	√	√	√	√	√	√	√	√	-