Azure Cosmos DB’s API for MongoDB: supported features and syntax

Azure Cosmos DB is Microsoft's globally distributed multi-model database service. You can communicate with the Azure Cosmos DB's API for MongoDB using any of the open source MongoDB client drivers. The Azure Cosmos DB's API for MongoDB enables the use of existing client drivers by adhering to the MongoDB wire protocol.

By using the Azure Cosmos DB's API for MongoDB, you can enjoy the benefits of the MongoDB you're used to, with all of the enterprise capabilities that Cosmos DB provides: global distribution, automatic sharding, availability and latency guarantees, automatic indexing of every field, encryption at rest, backups, and much more.

Protocol Support

The Azure Cosmos DB's API for MongoDB is compatible with MongoDB server version 3.2 by default. The supported operators and any limitations or exceptions are listed below. Features or query operators added in MongoDB version 3.4 are currently available as a preview feature. Any client driver that understands these protocols should be able to connect to Azure Cosmos DB's API for MongoDB.

The MongoDB aggregation pipeline is also currently available as a separate preview feature.

Query language support

Azure Cosmos DB's API 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's API for MongoDB supports the following database commands:

Query and write operation commands

  • delete
  • find
  • findAndModify
  • getLastError
  • getMore
  • insert
  • update

Authentication commands

  • logout
  • authenticate
  • getnonce

Administration commands

  • dropDatabase
  • listCollections
  • drop
  • create
  • filemd5
  • createIndexes
  • listIndexes
  • dropIndexes
  • connectionStatus
  • reIndex

Diagnostics commands

  • buildInfo
  • collStats
  • dbStats
  • hostInfo
  • listDatabases
  • whatsmyuri

Aggregation pipeline

Cosmos DB supports aggregation pipeline in public preview. See the Azure blog for instructions on how to onboard to the public preview.

Aggregation commands

  • aggregate
  • count
  • distinct

Aggregation stages

  • $project
  • $match
  • $limit
  • $skip
  • $unwind
  • $group
  • $sample
  • $sort
  • $lookup
  • $out
  • $count
  • $addFields

Aggregation expressions

Boolean expressions

  • $and
  • $or
  • $not

Set expressions

  • $setEquals
  • $setIntersection
  • $setUnion
  • $setDifference
  • $setIsSubset
  • $anyElementTrue
  • $allElementsTrue

Comparison expressions

  • $cmp
  • $eq
  • $gt
  • $gte
  • $lt
  • $lte
  • $ne

Arithmetic expressions

  • $abs
  • $add
  • $ceil
  • $divide
  • $exp
  • $floor
  • $ln
  • $log
  • $log10
  • $mod
  • $multiply
  • $pow
  • $sqrt
  • $subtract
  • $trunc

String expressions

  • $concat
  • $indexOfBytes
  • $indexOfCP
  • $split
  • $strLenBytes
  • $strLenCP
  • $strcasecmp
  • $substr
  • $substrBytes
  • $substrCP
  • $toLower
  • $toUpper

Array expressions

  • $arrayElemAt
  • $concatArrays
  • $filter
  • $indexOfArray
  • $isArray
  • $range
  • $reverseArray
  • $size
  • $slice
  • $in

Date expressions

  • $dayOfYear
  • $dayOfMonth
  • $dayOfWeek
  • $year
  • $month
  • $week
  • $hour
  • $minute
  • $second
  • $millisecond
  • $isoDayOfWeek
  • $isoWeek

Conditional expressions

  • $cond
  • $ifNull

Aggregation accumulators

  • $sum
  • $avg
  • $first
  • $last
  • $max
  • $min
  • $push
  • $addToSet

Operators

Following operators are supported with corresponding examples of their use. Consider this sample document used in the queries below:

{
  "Volcano Name": "Rainier",
  "Country": "United States",
  "Region": "US-Washington",
  "Location": {
    "type": "Point",
    "coordinates": [
      -121.758,
      46.87
    ]
  },
  "Elevation": 4392,
  "Type": "Stratovolcano",
  "Status": "Dendrochronology",
  "Last Known Eruption": "Last known eruption from 1800-1899, inclusive"
}
Operator Example
$eq { "Volcano Name": { $eq: "Rainier" } } -
$gt { "Elevation": { $gt: 4000 } } -
$gte { "Elevation": { $gte: 4392 } } -
$lt { "Elevation": { $lt: 5000 } } -
$lte { "Elevation": { $lte: 5000 } } -
$ne { "Elevation": { $ne: 1 } } -
$in { "Volcano Name": { $in: ["St. Helens", "Rainier", "Glacier Peak"] } } -
$nin { "Volcano Name": { $nin: ["Lassen Peak", "Hood", "Baker"] } } -
$or { $or: [ { Elevation: { $lt: 4000 } }, { "Volcano Name": "Rainier" } ] } -
$and { $and: [ { Elevation: { $gt: 4000 } }, { "Volcano Name": "Rainier" } ] } -
$not { "Elevation": { $not: { $gt: 5000 } } } -
$nor { $nor: [ { "Elevation": { $lt: 4000 } }, { "Volcano Name": "Baker" } ] } -
$exists { "Status": { $exists: true } } -
$type { "Status": { $type: "string" } } -
$mod { "Elevation": { $mod: [ 4, 0 ] } } -
$regex { "Volcano Name": { $regex: "^Rain"} } -

Notes

In $regex queries, Left-anchored expressions allow index search. However, using 'i' modifier (case-insensitivity) and 'm' modifier (multiline) causes the collection scan in all expressions. When there's a need to include '$' or '|', it is 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/}] }).

Update operators

Field update operators

  • $inc
  • $mul
  • $rename
  • $setOnInsert
  • $set
  • $unset
  • $min
  • $max
  • $currentDate

Array update operators

  • $addToSet
  • $pop
  • $pullAll
  • $pull (Note: $pull with condition is not supported)
  • $pushAll
  • $push
  • $each
  • $slice
  • $sort
  • $position

Bitwise update operator

  • $bit

Geospatial operators

Operator Example
$geoWithin { "Location.coordinates": { $geoWithin: { $centerSphere: [ [ -121, 46 ], 5 ] } } } Yes
$geoIntersects { "Location.coordinates": { $geoIntersects: { $geometry: { type: "Polygon", coordinates: [ [ [ -121.9, 46.7 ], [ -121.5, 46.7 ], [ -121.5, 46.9 ], [ -121.9, 46.9 ], [ -121.9, 46.7 ] ] ] } } } } Yes
$near { "Location.coordinates": { $near: { $geometry: { type: "Polygon", coordinates: [ [ [ -121.9, 46.7 ], [ -121.5, 46.7 ], [ -121.5, 46.9 ], [ -121.9, 46.9 ], [ -121.9, 46.7 ] ] ] } } } } Yes
$nearSphere { "Location.coordinates": { $nearSphere : [ -121, 46 ], $maxDistance: 0.50 } } Yes
$geometry { "Location.coordinates": { $geoWithin: { $geometry: { type: "Polygon", coordinates: [ [ [ -121.9, 46.7 ], [ -121.5, 46.7 ], [ -121.5, 46.9 ], [ -121.9, 46.9 ], [ -121.9, 46.7 ] ] ] } } } } Yes
$minDistance { "Location.coordinates": { $nearSphere : { $geometry: {type: "Point", coordinates: [ -121, 46 ]}, $minDistance: 1000, $maxDistance: 1000000 } } } Yes
$maxDistance { "Location.coordinates": { $nearSphere : [ -121, 46 ], $maxDistance: 0.50 } } Yes
$center { "Location.coordinates": { $geoWithin: { $center: [ [-121, 46], 1 ] } } } Yes
$centerSphere { "Location.coordinates": { $geoWithin: { $centerSphere: [ [ -121, 46 ], 5 ] } } } Yes
$box { "Location.coordinates": { $geoWithin: { $box: [ [ 0, 0 ], [ -122, 47 ] ] } } } Yes
$polygon { "Location.coordinates": { $near: { $geometry: { type: "Polygon", coordinates: [ [ [ -121.9, 46.7 ], [ -121.5, 46.7 ], [ -121.5, 46.9 ], [ -121.9, 46.9 ], [ -121.9, 46.7 ] ] ] } } } } Yes

Sort Operations

When using the findOneAndUpdate operation, sort operations on a single field are supported but sort operations on multiple fields are not supported.

Additional operators

Operator Example Notes
$all { "Location.coordinates": { $all: [-121.758, 46.87] } }
$elemMatch { "Location.coordinates": { $elemMatch: { $lt: 0 } } }
$size { "Location.coordinates": { $size: 2 } }
$comment { "Location.coordinates": { $elemMatch: { $lt: 0 } }, $comment: "Negative values"}
$text Not supported. Use $regex instead.

Unsupported operators

The $where and the $eval operators are not supported by Azure Cosmos DB.

Methods

Following methods are supported:

Cursor methods

Method Example Notes
cursor.sort() cursor.sort({ "Elevation": -1 }) Documents without sort key do not get returned

Unique indexes

Cosmos DB indexes every field in documents that are written to the database by default. Unique indexes ensure that a specific field doesn’t have duplicate values across all documents in a collection, similar to the way uniqueness is preserved on the default "_id" key. You can create custom indexes in Cosmos DB by using the createIndex command, including the 'unique’ constraint.

Unique indexes are available for all Cosmos accounts using Azure Cosmos DB's API for MongoDB.

Time-to-live (TTL)

Cosmos DB supports a time-to-live (TTL) based on the timestamp of the document. TTL can be enabled for collections by going to the Azure portal.

User and role management

Cosmos DB does not yet support users and roles. However, Cosmos DB supports role based access control (RBAC) and read-write and read-only passwords/keys that can be obtained through the Azure portal (Connection String page).

Replication

Cosmos DB supports automatic, native replication at the lowest layers. This logic is extended out to achieve low-latency, global replication as well. Cosmos DB does not support manual replication commands.

Write Concern

Some applications rely on a Write Concern which specifies the number of responses required during a write operation. Due to how Cosmos DB handles replication in the background all writes are all 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.

Sharding

Cosmos DB supports automatic, server-side sharding. Cosmos DB does not support manual sharding commands.

Next steps

  • Learn how to use Studio 3T with Azure Cosmos DB's API for MongoDB.
  • Learn how to use Robo 3T with Azure Cosmos DB's API for MongoDB.
  • Explore MongoDB samples with Azure Cosmos DB's API for MongoDB.

Note: This article describes a feature of Azure Cosmos DB that provides wire protocol compatibility with MongoDB databases. Microsoft does not run MongoDB databases to provide this service. Azure Cosmos DB is not affiliated with MongoDB, Inc.