CRUD & Aggregation APIs

On this page

Overview

CRUD Operations
Query Operators
Update Operators
Bulk Write Operations
Query Options
Aggregation
Aggregation Methods
Aggregation Pipeline Stage Availability
Aggregation Pipeline Operator Availability
Database Commands
Database Command Availability

Overview

This page lists MongoDB data source support for MongoDB commands, operators, options, and aggregation stages.

For information on how to read and write data in MongoDB from a function, see Query MongoDB Atlas.

For more information on supported features and limitations, see Service Limitations.

Note

Support for an operation may depend on whether you're running the operation as an application user or as a system user.

A user function runs in the context of a specific application user and enforces data access permissions and schema validation, which makes some operations untenable.
A system function runs as a generic system user and is not subject to rules or schema validation. Some operations are only available in system functions.

CRUD Operations

Query Operators

MongoDB Realm supports most query operators for queries that run in a user function. However, some evaluation operators and all geospatial and bitwise operators are only available in system functions.

Comparison Operator Availability

Operation	User Function	System Function
$eq	Yes	Yes
$gt	Yes	Yes
$gte	Yes	Yes
$in	Yes	Yes
$lt	Yes	Yes
$lte	Yes	Yes
$ne	Yes	Yes
$nin	Yes	Yes

Logical Operator Availability

Operation	User Function	System Function
$and	Yes	Yes
$not	Yes	Yes
$nor	Yes	Yes
$or	Yes	Yes

Array Operator Availability

Operation	User Function	System Function
$all	Yes	Yes
$elemMatch	Yes	Yes
$size	Yes	Yes

Element Operator Availability

Operation	User Function	System Function
$exists	Yes	Yes
$type	Yes	Yes

Evaluation Operator Availability

Operation	User Function	System Function
$mod	Yes	Yes
$expr	No	Yes
$jsonSchema	No	Yes
$regex	No	Yes
$text	No	Yes
$where	No	Yes

Geospatial Operator Availability

Operation	User Function	System Function
$geoIntersects	No	Yes
$geoWithin	No	Yes
$near	No	Yes
$nearSphere	No	Yes

Bitwise Operator Availability

Operation	User Function	System Function
$bitsAllClear	No	Yes
$bitsAllSet	No	Yes
$bitsAnyClear	No	Yes
$bitsAnySet	No	Yes

Update Operators

MongoDB Realm supports most update operators for queries that run in a user function. However, some array update operators are only available in system functions.

Field Update Operator Availability

Operation	User Function	System Function
$currentDate	Yes	Yes
$inc	Yes	Yes
$min	Yes	Yes
$max	Yes	Yes
$mul	Yes	Yes
$rename	Yes	Yes
$set	Yes	Yes
$setOnInsert	Yes	Yes
$unset	Yes	Yes

Array Update Operator Availability

Operation	User Function	System Function
$ (Positional Update)	Yes	Yes
$addToSet	Yes	Yes
$pop	Yes	Yes
$pull	Yes	Yes
$push	Yes	Yes
$pullAll	Yes	Yes
$[] (All Positional Update)	Yes	Yes
$[element] (Filtered Positional Update)	Yes	Yes

Array Update Operator Modifiers Availability

Modifier	User Function	System Function
$each	Yes	Yes
$position	Yes	Yes
$slice	Yes	Yes
$sort	Yes	Yes

Bitwise Update Operator Availability

Operator	User Function	System Function
$bit	Yes	Yes

Bulk Write Operations

MongoDB Realm supports bulk write operations using the same API as the MongoDB Node.js driver.

Tip

Realm also provides the collection.bulkWrite() method for performing bulk write operations.

Ordered Bulk Write Operation Availability

You define ordered bulk operations by calling collection.initializeOrderedBulkOp() and manipulating the OrderedBulkOperation object that it returns.

Realm supports the following OrderedBulkOperation methods:

Operation	User Function	System Function
execute	Yes	Yes
find	Yes	Yes
insert	Yes	Yes

Unordered Bulk Write Operation Availability

You define unordered bulk operations by calling collection.initializeUnorderedBulkOp() and manipulating the OrderedBulkOperation object that it returns.

Realm supports the following UnorderedBulkOperation methods:

Operation	User Function	System Function
execute	Yes	Yes
find	Yes	Yes
insert	Yes	Yes

Query Options

MongoDB Realm does not support configuring the following options for any CRUD operation in user functions. All query options are available in system functions.

Query Option Availability

Option	User Context	System Context
Read Isolation (Read Concern)	No	Yes
Write Acknowledgment (Write Concern)	No	Yes
Collation	No	Yes

Aggregation

Aggregation Methods

MongoDB Realm supports aggregation on the both the database and collection level using the following commands:

Aggregation Pipeline Stage Availability

MongoDB Realm does not support the following aggregation pipeline stages when you run an aggregation pipeline in the context of an application user. All aggregation pipeline stages are available to the system user except for $indexStats.

Stage	User Context	System Context
$collStats	No	Yes
$currentOp	No	Yes
$facet	No	Yes
$geoNear	No	Yes
$graphLookup	No	Yes
$indexStats	No	No
$lookup	Yes	Yes
$merge	No	Yes
$out	No	Yes
$search Important Realm performs `$search` operations as a system user and enforces field-level rules on the returned search results. This means that a user may search on a field for which they do not have read access. In this case, the search is based on the specified field but no returned documents include the field.	Yes	Yes
$unionWith	Yes	Yes

Note

By default, $merge and $out route the entire aggregation operation to the cluster's primary node. If you want to force these stages to respect your configured cluster read preference, set the enforceReadPref option to true.

Aggregation Pipeline Operator Availability

MongoDB Realm supports all aggregation pipeline operators when you run an aggregation pipeline in the system user context. Realm supports all pipeline operators in an application user context with the following exceptions:

Operator	User Context	System Context
$function	No	Yes

Database Commands

MongoDB Realm does not support any database commands in the Client SDKs or Functions. You can, however, call a limited subset of database commands when connected to a MongoDB cluster over the MongoDB Realm wire protocol.

The following database commands are partially supported over the wire protocol. Unsupported options for each command are listed below.

Note

Realm apps cannot run commands on the admin database.

Database Command Availability

Command	Unsupported Options	Realm-Specific Options
find	`hint` `skip` `batchSize` `comment` `maxScan` `maxTimeMS` `readConcern` `max` `min` `returnKey` `showRecordId` `tailable` `awaitData` `oplogReplay` `noCursorTimeout` `allowPartialResults` `collation`
aggregate	`explain` `allowDiskUse` `maxTimeMS` `readConcern` `collation` `bypassDocumentValidation` `hint` `comment` `writeConcern`	`enforceReadPref`
count	`limit` `skip` `hint` `readConcern`
insert	`writeConcern` `bypassDocumentValidation`
update	`bypassDocumentValidation` `collation` `arrayFilters`
delete	`collation`

← MongoDB Data Sources Read Preference →