Azure Cosmos DB for MongoDB (4.0 server version): supported features and syntax
Article
APPLIES TO:
MongoDB
Azure Cosmos DB is Azure's multiple-regionally distributed multi-model database service. You can communicate with the Azure Cosmos DB for MongoDB using any of the open-source MongoDB client drivers. The Azure Cosmos DB for MongoDB enables the use of existing client drivers by adhering to the MongoDB wire protocol.
By using the Azure Cosmos DB for MongoDB, you can enjoy the benefits of the MongoDB you're used to, with all of the enterprise capabilities that Azure Cosmos DB provides: multiple-region distribution, automatic sharding, availability and latency guarantees, encryption at rest, backups, and much more.
Protocol Support
The supported operators and any limitations or exceptions are listed below. Any client driver that understands these protocols should be able to connect to Azure Cosmos DB for MongoDB. When you create Azure Cosmos DB for MongoDB accounts, the 3.6+ versions of accounts have the endpoint in the format *.mongo.cosmos.azure.cn whereas the 3.2 version of accounts has the endpoint in the format *.documents.azure.cn.
Note
This article only lists the supported server commands and excludes client-side wrapper functions. Client-side wrapper functions such as deleteMany() and updateMany() internally utilize the delete() and update() server commands. Functions utilizing supported server commands are compatible with Azure Cosmos DB for MongoDB.
Query language support
Azure Cosmos DB for MongoDB provides comprehensive support for MongoDB query language constructs. Below you can find the detailed list of currently supported operations, operators, stages, commands, and options.
Database commands
Azure Cosmos DB for MongoDB supports the following database commands:
$lookup does not yet support the uncorrelated subqueries feature introduced in server version 3.6. You will receive an error with a message containing let is not supported if you attempt to use the $lookup operator with let and pipeline fields.
Boolean expressions
Command
Supported
and
Yes
not
Yes
or
Yes
Conversion expressions
Command
Supported
convert
Yes
toBool
Yes
toDate
Yes
toDecimal
Yes
toDouble
Yes
toInt
Yes
toLong
Yes
toObjectId
Yes
toString
Yes
Set expressions
Command
Supported
setEquals
Yes
setIntersection
Yes
setUnion
Yes
setDifference
Yes
setIsSubset
Yes
anyElementTrue
Yes
allElementsTrue
Yes
Comparison expressions
Note
The API for MongoDB does not support comparison expressions with an array literal in the query.
Command
Supported
cmp
Yes
eq
Yes
gt
Yes
gte
Yes
lt
Yes
lte
Yes
ne
Yes
in
Yes
nin
Yes
Arithmetic expressions
Command
Supported
abs
Yes
add
Yes
ceil
Yes
divide
Yes
exp
Yes
floor
Yes
ln
Yes
log
Yes
log10
Yes
mod
Yes
multiply
Yes
pow
Yes
sqrt
Yes
subtract
Yes
trunc
Yes
String expressions
Command
Supported
concat
Yes
indexOfBytes
Yes
indexOfCP
Yes
ltrim
Yes
rtrim
Yes
trim
Yes
split
Yes
strLenBytes
Yes
strLenCP
Yes
strcasecmp
Yes
substr
Yes
substrBytes
Yes
substrCP
Yes
toLower
Yes
toUpper
Yes
Text search operator
Command
Supported
meta
No
Array expressions
Command
Supported
arrayElemAt
Yes
arrayToObject
Yes
concatArrays
Yes
filter
Yes
indexOfArray
Yes
isArray
Yes
objectToArray
Yes
range
Yes
reverseArray
Yes
reduce
Yes
size
Yes
slice
Yes
zip
Yes
in
Yes
Variable operators
Command
Supported
map
Yes
let
Yes
System variables
Command
Supported
$$CURRENT
Yes
$$DESCEND
Yes
$$KEEP
Yes
$$PRUNE
Yes
$$REMOVE
Yes
$$ROOT
Yes
Literal operator
Command
Supported
literal
Yes
Date expressions
Command
Supported
dayOfYear
Yes
dayOfMonth
Yes
dayOfWeek
Yes
year
Yes
month
Yes
week
Yes
hour
Yes
minute
Yes
second
Yes
millisecond
Yes
dateToString
Yes
isoDayOfWeek
Yes
isoWeek
Yes
dateFromParts
Yes
dateToParts
Yes
dateFromString
Yes
isoWeekYear
Yes
Conditional expressions
Command
Supported
cond
Yes
ifNull
Yes
switch
Yes
Data type operator
Command
Supported
type
Yes
Accumulator expressions
Command
Supported
sum
Yes
avg
Yes
first
Yes
last
Yes
max
Yes
min
Yes
push
Yes
addToSet
Yes
stdDevPop
Yes
stdDevSamp
Yes
Merge operator
Command
Supported
mergeObjects
Yes
Data types
Azure Cosmos DB for MongoDB supports documents encoded in MongoDB BSON format. The 4.0 API version enhances the internal usage of this format to improve performance and reduce costs. Documents written or updated through an endpoint running 4.0+ benefit from optimization.
In an upgrade scenario, documents written prior to the upgrade to version 4.0+ won't benefit from the enhanced performance until they're updated via a write operation through the 4.0+ endpoint.
16-MB document support raises the size limit for your documents from 2 MB to 16 MB. This limit only applies to collections created after this feature has been enabled. Once this feature is enabled for your database account, it can't be disabled.
We recommend enabling Server Side Retry and avoiding wildcard indexes to ensure requests with larger documents succeed. If necessary, raising your DB/Collection RUs may also help performance.
Command
Supported
Double
Yes
String
Yes
Object
Yes
Array
Yes
Binary Data
Yes
ObjectId
Yes
Boolean
Yes
Date
Yes
Null
Yes
32-bit Integer (int)
Yes
Timestamp
Yes
64-bit Integer (long)
Yes
MinKey
Yes
MaxKey
Yes
Decimal128
Yes
Regular Expression
Yes
JavaScript
Yes
JavaScript (with scope)
Yes
Undefined
Yes
Indexes and index properties
Indexes
Command
Supported
Single Field Index
Yes
Compound Index
Yes
Multikey Index
Yes
Text Index
No
2dsphere
Yes
2d Index
No
Hashed Index
No
Index properties
Command
Supported
TTL
Yes
Unique
Yes
Partial
No
Case Insensitive
No
Sparse
No
Background
Yes
Operators
Logical operators
Command
Supported
or
Yes
and
Yes
not
Yes
nor
Yes
Element operators
Command
Supported
exists
Yes
type
Yes
Evaluation query operators
Command
Supported
expr
Yes
jsonSchema
No
mod
Yes
regex
Yes
text
No (Not supported. Use $regex instead.)
where
No
In the $regex queries, left-anchored expressions allow index search. However, using 'i' modifier (case-insensitivity) and 'm' modifier (multiline) causes the collection scan in all expressions.
When there's a need to include '$' or '|', it's best to create two (or more) regex queries. For example, given the following original query: find({x:{$regex: /^abc$/}), it has to be modified as follows:
find({x:{$regex: /^abc/, x:{$regex:/^abc$/}})
The first part will use the index to restrict the search to those documents beginning with ^abc and the second part will match the exact entries. The bar operator '|' acts as an "or" function - the query find({x:{$regex: /^abc |^def/}) matches the documents in which field 'x' has values that begin with "abc" or "def". To utilize the index, it's recommended to break the query into two different queries joined by the $or operator: find( {$or : [{x: $regex: /^abc/}, {$regex: /^def/}] }).
Array operators
Command
Supported
all
Yes
elemMatch
Yes
size
Yes
Comment operator
Command
Supported
comment
Yes
Projection operators
Command
Supported
elemMatch
Yes
meta
No
slice
Yes
Update operators
Field update operators
Command
Supported
inc
Yes
mul
Yes
rename
Yes
setOnInsert
Yes
set
Yes
unset
Yes
min
Yes
max
Yes
currentDate
Yes
Array update operators
Command
Supported
$
Yes
$[]
Yes
$[\<identifier\>]
Yes
addToSet
Yes
pop
Yes
pullAll
Yes
pull
Yes
push
Yes
pushAll
Yes
Update modifiers
Command
Supported
each
Yes
slice
Yes
sort
Yes
position
Yes
Bitwise update operator
Command
Supported
bit
Yes
bitsAllSet
No
bitsAnySet
No
bitsAllClear
No
bitsAnyClear
No
Geospatial operators
Operator
Supported
$geoWithin
Yes
$geoIntersects
Yes
$near
Yes
$nearSphere
Yes
$geometry
Yes
$minDistance
Yes
$maxDistance
Yes
$center
No
$centerSphere
No
$box
No
$polygon
No
Sort operations
When you use the findOneAndUpdate operation with API for MongoDB version 4.0, sort operations on a single field and multiple fields are supported. Sort operations on multiple fields were a limitation of previous wire protocols.
Indexing
The API for MongoDB supports various indexes to enable sorting on multiple fields, improve query performance, and enforce uniqueness.
GridFS
Azure Cosmos DB supports GridFS through any GridFS-compatible Mongo driver.
Replication
Azure Cosmos DB supports automatic, native replication at the lowest layers. This logic is extended out to achieve low-latency, multiple-region replication as well. Azure Cosmos DB doesn't support manual replication commands.
Retryable Writes
Retryable writes enable MongoDB drivers to automatically retry certain write operations if there was failure, but results in more stringent requirements for certain operations, which match MongoDB protocol requirements. With this feature enabled, update operations, including deletes, in sharded collections will require the shard key to be included in the query filter or update statement.
For example, with a sharded collection, sharded on key “country”: To delete all the documents with the field city = "Shanghai", the application will need to execute the operation for all shard key (country) values if Retryable writes are enabled.
db.coll.deleteMany({"city": "Shanghai"}) - Fails with error ShardKeyNotFound(61)
Note
Retryable writes does not support bulk unordered writes at this time. If you would like to perform bulk writes with retryable writes enabled, perform bulk ordered writes.
Azure Cosmos DB supports automatic, server-side sharding. It manages shard creation, placement, and balancing automatically. Azure Cosmos DB doesn't support manual sharding commands, which means you don't have to invoke commands such as addShard, balancerStart, moveChunk etc. You only need to specify the shard key while creating the containers or querying the data.
Sessions
Azure Cosmos DB doesn't yet support server-side sessions commands.
Time-to-live (TTL)
Azure Cosmos DB supports a time-to-live (TTL) based on the timestamp of the document. TTL can be enabled for collections from the Azure portal.
Transactions
Multi-document transactions are supported within an unsharded collection. Multi-document transactions aren't supported across collections or in sharded collections. The timeout for transactions is a fixed 5 seconds.
User and role management
Azure Cosmos DB doesn't yet support users and roles. However, Azure Cosmos DB supports Azure role-based access control (Azure RBAC) and read-write and read-only passwords/keys that can be obtained through the Azure portal (Connection String page).
Write Concern
Some applications rely on a Write Concern, which specifies the number of responses required during a write operation. Due to how Azure Cosmos DB handles replication in the background all writes are automatically Quorum by default. Any write concern specified by the client code is ignored. Learn more in Using consistency levels to maximize availability and performance.
Next steps
Learn how to use Studio 3T with Azure Cosmos DB for MongoDB.
Learn how to use Robo 3T with Azure Cosmos DB for MongoDB.
Explore MongoDB samples with Azure Cosmos DB for MongoDB.
Trying to do capacity planning for a migration to Azure Cosmos DB? You can use information about your existing database cluster for capacity planning.
MongoDB