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MongoDB Service Limitations

Overview

You can access most of the CRUD and Aggregation functionality of MongoDB version 3.6 with the MongoDB service; however, Stitch does not support all operations and features available in standard tools and clients. This page lists MongoDB features that are not available when you connect to MongoDB through Stitch.

System Users

The CRUD API and Aggregation Framework limitations on this page do not apply to queries executed from a System Function.

Notable Unsupported Features

• Transactions
• Most database commands and administrative features.
• Change Streams
  • For an alternative to change streams, see Triggers, Watch, and Mobile Sync.
  • Triggers, Watch, and Mobile Sync use change streams on a linked cluster to listen for changes. See the Change Streams section of this page for limitations that apply to these features.

CRUD Operations

Query Results

MongoDB queries executed through Stitch can return a maximum of 50,000 documents. If you need to return more documents, consider paginating your query.

Query Operators

System Users

Stitch supports all query operators, including those listed in this section, when you execute a query from a System Function.

Stitch supports most query operators but does not support some operator types for queries that run in the context of an application user. Refer to the following table for details on a specific type of operator:

Operator Type	Supported	Unsupported
Comparison Operators	$eq $gt $gte $in $lt $lte $ne $nin	No unsupported operators
Logical Operators	$and $not $nor $or	No unsupported operators
Array Operators	$all $elemMatch $size	No unsupported operators
Element Operators	$exists $type	No unsupported operators
Evaluation Operators	$mod	$expr $jsonSchema $regex $text $where
Geospatial Operators	No supported operators	$geoIntersects $geoWithin $near $nearSphere
Bitwise Operators	No supported operators	$bitsAllClear $bitAllSet $bitsAnyClear $bitsAnySet

Update Operators

System Users

Stitch supports all update operators, including those listed in this section, when you execute a query from a System Function.

Stitch supports most update operators but does not support some operators for updates that run in the context of an application user. Refer to the following table for details on a specific operator:

Operator Type	Supported	Unsupported
Field Update Operators	$currentDate $inc $min $max $mul $rename $set $setOnInsert $unset	No unsupported operators
Array Update Operators	$ (Positional Update) $addToSet $pop $pull $push $pullAll	$[] (All Positional Update) $[element] (Filtered Positional Update)
Array Update Modifiers	$each $position $slice $sort $bit	No unsupported operators
Array Update Modifiers	$each $position $slice $sort	No unsupported operators

Bulk Write Operations

System Users

Stitch supports all bulk write operations, including those listed in this section, when you execute the operation from a System Function.

Stitch does not support most bulk write operations. Refer to the following table for details on a specific bulk write operation:

Bulk Operation	Supported	Notes
insertOne/insertMany	Yes	Bulk insert operations through Stitch are always ordered. If any insert in an ordered bulk operation fails, the operation returns immediately without inserting any more documents.
updateOne/updateMany	No
deleteOne/deleteMany	No

Query Options

System Users

Stitch supports all query options, including those listed in this section, when you execute a query from a System Function.

Stitch does not support configuring the following options for any CRUD operation:

• Read Isolation (Read Concern)
• Write Acknowledgmenet (Write Concern).
• Collation

Aggregation Framework

Aggregation Stages

System Users

Stitch supports all aggregation stages, including those listed in this section, when you run a pipeline from a System Function.

Stitch does not support the following aggregation pipeline stages when you run an aggregation pipeline in the context of an application user:

• $collStats
• $currentOp
• $lookup
• $out
• $indexStats
• $facet
• $graphLookup
• $text
• $geoNear

Administration

Database Commands

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

The following database commands are partially supported over the wire protocol:

Command	Details
find	The following find command options are not supported: hint skip batchSize comment maxScan maxTimeMS readConcern max min returnKey showRecordId tailable awaitData oplogReplay noCursorTimeout allowPartialResults collation
aggregate	The following aggregate command options are not supported: explain allowDiskUse maxTimeMS readConcern collation bypassDocumentValidation hint comment writeConcern
count	The following count command options are not supported: limit skip hint readConcern
insert	The following insert command options are not supported: writeConcern bypassDocumentValidation
update	The following update command options are not supported: bypassDocumentValidation collation arrayFilters
delete	The following delete command options are not supported: collation

Change Streams

Stitch limits the total number of change streams open against a given cluster across all Stitch apps based on the cluster’s size. It also limits the number of client applications that can concurrently listen for changes using Watch and Mobile Sync. The following table lists the limitations for each cluster size:

Cluster Size	Maximum Number of Change Streams	Maximum Number of Concurrent Listening Clients
Free Tier (M0)	5	250
Shared Clusters (M2/M5)	10	500
Small, Dedicated Clusters (M10/M20)	100	1000
Standard Clusters (M30/M40)	1000	10000
Standard Clusters (M50 - M90)	1000	50000
High-Power Clusters (M100+)	1000	100000 (Contact Support for Additional Usage)

Note

Stitch opens a single change stream on each collection that is associated with a Database Trigger, Collection Sync, or Watch operation.

Usage Recommendation

To minimize the number of concurrent listening clients and open change streams:

• Start Watch and Sync operations only when necessary. Close any open Watch and Sync streams immediately when they’re no longer necessary.
• Avoid data models that require you to Watch or Sync an unbounded number of collections.

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