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db.createCollection()

On this page

  • Definition
  • Compatibility
  • Syntax
  • Access Control
  • Behavior
  • Examples

Definition

db.createCollection(name, options)

Creates a new collection. For views, see db.createView().

Because MongoDB creates a collection implicitly when the collection is first referenced in a command, this method is used primarily for creating new collections that use specific options. For example, you use db.createCollection() to create a:

db.createCollection() is a wrapper around the database command create.

Compatibility

You can use db.createCollection() for deployments hosted in the following environments:

  • MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

Syntax

The db.createCollection() method has the following prototype form:

db.createCollection( <name>,
    {
      capped: <boolean>,
      timeseries: {                  // Added in MongoDB 5.0
         timeField: <string>,        // required for time series collections
         metaField: <string>,
         granularity: <string>,
         bucketMaxSpanSeconds: <number>,  // Added in MongoDB 6.3
         bucketRoundingSeconds: <number>  // Added in MongoDB 6.3
      },
      expireAfterSeconds: <number>,
      clusteredIndex: <document>,  // Added in MongoDB 5.3
      changeStreamPreAndPostImages: <document>,  // Added in MongoDB 6.0
      size: <number>,
      max: <number>,
      storageEngine: <document>,
      validator: <document>,
      validationLevel: <string>,
      validationAction: <string>,
      indexOptionDefaults: <document>,
      viewOn: <string>,
      pipeline: <pipeline>,
      collation: <document>,
      writeConcern: <document>
    }
  )

The db.createCollection() method has the following parameters:

Parameter
Type
Description
name
string
The name of the collection to create. See Naming Restrictions.
options
document

Optional. Configuration options for creating a:

  • Capped collection

  • Clustered collection

  • View

The options document contains the following fields:

Field
Type
Description
capped
boolean
Optional. To create a capped collection, specify true. If you specify true, you must also set a maximum size in the size field.
timeseries.timeField
string
Required when creating a time series collection. The name of the field which contains the date in each time series document. Documents in a time series collection must have a valid BSON date as the value for the timeField.
timeseries.metaField
string

Optional. The name of the field which contains metadata in each time series document. The metadata in the specified field should be data that is used to label a unique series of documents. The metadata should rarely, if ever, change.

The name of the specified field may not be _id or the same as the timeseries.timeField. The field can be of any type except array.

timeseries.granularity
string

Optional, do not use if setting bucketRoundingSeconds and bucketMaxSpanSeconds. Possible values are seconds (default), minutes, and hours.

Set granularity to the value that most closely matches the time between consecutive incoming timestamps. This improves performance by optimizing how MongoDB internally stores data in the collection.

For more information on granularity and bucket intervals, see Set Granularity for Time Series Data.

timeseries.bucketMaxSpanSeconds
integer

Optional, used with bucketRoundingSeconds as an alternative to granularity. Sets the maximum time between timestamps in the same bucket. Possible values are 1-31536000. If you set bucketMaxSpanSeconds, you must set bucketRoundingSeconds to the same value.

To downgrade below MongoDB 6.3, you must either modify the collection to use the corresponding granularity value, or drop the collection. For details, see collMod.

timeseries.bucketRoundingSeconds
integer

Optional, used with bucketMaxSpanSeconds as an alternative to granularity. Sets the number of seconds to round down by when MongoDB sets the minimum timestamp for a new bucket. Must be equal to bucketMaxSpanSeconds.

For example, setting both parameters to 1800 rounds new buckets down to the nearest 30 minutes. If a document with a time of 2023-03-27T18:24:35Z does not fit an existing bucket, MongoDB creates a new bucket with a minimum time of 2023-03-27T18:00:00Z and a maximum time of 2023-03-27T18:30:00Z.

expireAfterSeconds
number

Optional. Specifies the seconds after which documents in a time series collection or clustered collection expire. MongoDB deletes expired documents automatically.

For clustered collections, the documents are deleted automatically based on the clustered index key _id and the values must be date types. See TTL Indexes.

clusteredIndex
document

Starting in MongoDB 5.3, you can create a collection with a clustered index. Collections created with a clustered index are called clustered collections.

See Clustered Collections.

clusteredIndex has the following syntax:

clusteredIndex: {
   key: { <string> },
   unique: <boolean>,
   name: <string>
}
Field
Description
key
Required. The clustered index key field. Must be set to { _id: 1 }. The default value for the _id field is an automatically generated unique object identifier, but you can set your own clustered index key values.
unique
Required. Must be set to true. A unique index indicates the collection will not accept inserted or updated documents where the clustered index key value matches an existing value in the index.
name
Optional. A name that uniquely identifies the clustered index.

New in version 5.3.

changeStreamPreAndPostImages
document

Optional.

Starting in MongoDB 6.0, you can use change stream events to output the version of a document before and after changes (the document pre- and post-images):

  • The pre-image is the document before it was replaced, updated, or deleted. There is no pre-image for an inserted document.

  • The post-image is the document after it was inserted, replaced, or updated. There is no post-image for a deleted document.

  • Enable changeStreamPreAndPostImages for a collection using db.createCollection(), create, or collMod.

changeStreamPreAndPostImages has the following syntax:

changeStreamPreAndPostImages: {
   enabled: <boolean>
}
enabled
Description
true
Enables change stream pre- and post-images for a collection.
false
Disables change stream pre- and post-images for a collection.

For complete examples with the change stream output, see Change Streams with Document Pre- and Post-Images.

For a db.createCollection() example on this page, see Create a Collection with Change Stream Pre- and Post-Images for Documents.

New in version 6.0.

size
number
Optional. Specify a maximum size in bytes for a capped collection. Once a capped collection reaches its maximum size, MongoDB removes the older documents to make space for the new documents. The size field is required for capped collections and ignored for other collections.
max
number
Optional. The maximum number of documents allowed in the capped collection. The size limit takes precedence over this limit. If a capped collection reaches the size limit before it reaches the maximum number of documents, MongoDB removes old documents. If you prefer to use the max limit, ensure that the size limit, which is required for a capped collection, is sufficient to contain the maximum number of documents.
storageEngine
document

Optional. Available for the WiredTiger storage engine only.

Allows users to specify configuration to the storage engine on a per-collection basis when creating a collection. The value of the storageEngine option should take the following form:

{ <storage-engine-name>: <options> }

Storage engine configuration specified when creating collections are validated and logged to the oplog during replication to support replica sets with members that use different storage engines.

Tip

See also:

Specify Storage Engine Options

validator
document

Optional. Allows users to specify validation rules or expressions for the collection.

The validator option takes a document that specifies the validation rules or expressions. You can specify the expressions using the same operators as the query operators with the exception of $near, $nearSphere, $text, and $where.

To learn how to create a collection with schema validation, see Specify JSON Schema Validation.

validationLevel
string

Optional. Determines how strictly MongoDB applies the validation rules to existing documents during an update.

validationLevel
Description
"off"
No validation for inserts or updates.
"strict"
Default Apply validation rules to all inserts and all updates.
"moderate"
Apply validation rules to inserts and to updates on existing valid documents. Do not apply rules to updates on existing invalid documents.

To see an example that uses validationLevel, see Specify Validation Level for Existing Documents.

validationAction
string

Optional. Determines whether to error on invalid documents or just warn about the violations but allow invalid documents to be inserted.

Important

Validation of documents only applies to those documents as determined by the validationLevel.

To see an example that uses validationAction, see Choose How to Handle Invalid Documents.

indexOptionDefaults
document

Optional. Allows users to specify a default configuration for indexes when creating a collection.

The indexOptionDefaults option accepts a storageEngine document, which should take the following form:

{ <storage-engine-name>: <options> }

Storage engine configuration specified when creating indexes are validated and logged to the oplog during replication to support replica sets with members that use different storage engines.

viewOn
string
The name of the source collection or view from which to create a view. For details, see db.createView().
pipeline
array
An array that consists of the aggregation pipeline stage(s). db.createView() creates a view by applying the specified pipeline to the viewOn collection or view. For details, see db.createView().
collation
document

Specifies the default collation for the collection.

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.

The collation option has the following syntax:

collation: {
   locale: <string>,
   caseLevel: <boolean>,
   caseFirst: <string>,
   strength: <int>,
   numericOrdering: <boolean>,
   alternate: <string>,
   maxVariable: <string>,
   backwards: <boolean>
}

When specifying collation, the locale field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document.

If you specify a collation at the collection level:

  • Indexes on that collection will be created with that collation unless the index creation operation explicitly specify a different collation.

  • Operations on that collection use the collection's default collation unless they explicitly specify a different collation.

    You cannot specify multiple collations for an operation. For example, you cannot specify different collations per field, or if performing a find with a sort, you cannot use one collation for the find and another for the sort.

If no collation is specified for the collection or for the operations, MongoDB uses the simple binary comparison used in prior versions for string comparisons.

For a collection, you can only specify the collation during the collection creation. Once set, you cannot modify the collection's default collation.

For an example, see Specify Collation.

writeConcern
document

Optional. A document that expresses the write concern for the operation. Omit to use the default write concern.

When issued on a sharded cluster, mongos converts the write concern of the create command and its helper db.createCollection() to "majority".

Access Control

If the deployment enforces authentication/authorization, db.createCollection() requires the following privileges:

Task
Required Privileges
Create a non-capped collection

createCollection on the database, or

insert on the collection to create

convertToCapped for the collection

createCollection on the database

Create a view

createCollection on the database.

However, if the user has the createCollection on the database and find on the view to create, the user must also have the following additional permissions:

  • find on the source collection or view.

  • find on any other collections or views referenced in the pipeline, if any.

A user with the readWrite built in role on the database has the required privileges to run the listed operations. Either create a user with the required role or grant the role to an existing user.

Behavior

db.createCollection() has the following behavior:

Resource Locking

db.createCollection() obtains an exclusive lock on the specified collection or view for the duration of the operation. All subsequent operations on the collection must wait until db.createCollection() releases the lock. db.createCollection() typically holds this lock for a short time.

Creating a view requires obtaining an additional exclusive lock on the system.views collection in the database. This lock blocks creation or modification of views in the database until the command completes.

Transactions

You can create collections and indexes inside a distributed transaction if the transaction is not a cross-shard write transaction.

To use db.createCollection() in a transaction, the transaction must use read concern "local". If you specify a read concern level other than "local", the transaction fails.

Tip

See also:

Create Collections and Indexes in a Transaction

Collection or View with Same Name and Options

If you run db.createCollection() with the same name and options as an existing collection or view, db.createCollection() returns success.

Examples

Create a Capped Collection

Capped collections have maximum size or document counts that prevent them from growing beyond maximum thresholds. All capped collections must specify a maximum size and may also specify a maximum document count. MongoDB removes older documents if a collection reaches the maximum size limit before it reaches the maximum document count. Consider the following example:

db.createCollection("log", { capped : true, size : 5242880, max : 5000 } )

This command creates a collection named log with a maximum size of 5 megabytes and a maximum of 5000 documents.

See Capped Collections for more information about capped collections.

Create a Time Series Collection

To create a time series collection that captures weather data for the past 24 hours, issue this command:

db.createCollection(
    "weather24h",
    {
       timeseries: {
          timeField: "timestamp",
          metaField: "data",
          granularity: "hours"
       },
       expireAfterSeconds: 86400
    }
)

Alternately, to create the same collection but limit each bucket to timestamp values within the same hour, issue this command:

db.createCollection(
    "weather24h",
    {
       timeseries: {
          timeField: "timestamp",
          metaField: "data",
          bucketMaxSpanSeconds: "3600",
          bucketRoundingSeconds: "3600"
       },
       expireAfterSeconds: 86400
    }
)

Create a Clustered Collection

The following db.createCollection() example adds a clustered collection named stocks:

db.createCollection(
   "stocks",
   { clusteredIndex: { "key": { _id: 1 }, "unique": true, "name": "stocks clustered key" } }
)

In the example, clusteredIndex specifies:

  • "key": { _id: 1 }, which sets the clustered index key to the _id field.

  • "unique": true, which indicates the clustered index key value must be unique.

  • "name": "stocks clustered key", which sets the clustered index name.

Create a Collection with Change Stream Pre- and Post-Images for Documents

Starting in MongoDB 6.0, you can use change stream events to output the version of a document before and after changes (the document pre- and post-images):

  • The pre-image is the document before it was replaced, updated, or deleted. There is no pre-image for an inserted document.

  • The post-image is the document after it was inserted, replaced, or updated. There is no post-image for a deleted document.

  • Enable changeStreamPreAndPostImages for a collection using db.createCollection(), create, or collMod.

The following example creates a collection that has changeStreamPreAndPostImages enabled:

db.createCollection(
   "temperatureSensor",
   { changeStreamPreAndPostImages: { enabled: true } }
);

Pre- and post-images are not available for a change stream event if the images were:

  • Not enabled on the collection at the time of a document update or delete operation.

  • Removed after the pre- and post-image retention time set in expireAfterSeconds.

    • The following example sets expireAfterSeconds to 100 seconds:

      use admin
      db.runCommand( {
         setClusterParameter:
            { changeStreamOptions: { preAndPostImages: { expireAfterSeconds: 100 } } }
      } )

    • The following example returns the current changeStreamOptions settings, including expireAfterSeconds:

      db.adminCommand( { getClusterParameter: "changeStreamOptions" } )

    • Setting expireAfterSeconds to off uses the default retention policy: pre- and post-images are retained until the corresponding change stream events are removed from the oplog.

    • If a change stream event is removed from the oplog, then the corresponding pre- and post-images are also deleted regardless of the expireAfterSeconds pre- and post-image retention time.

Additional considerations:

  • Enabling pre- and post-images consumes storage space and adds processing time. Only enable pre- and post-images if you need them.

  • Limit the change stream event size to less than 16 megabytes. To limit the event size, you can:

    • Limit the document size to 8 megabytes. You can request pre- and post-images simultaneously in the change stream output if other change stream event fields like updateDescription are not large.

    • Request only post-images in the change stream output for documents up to 16 megabytes if other change stream event fields like updateDescription are not large.

    • Request only pre-images in the change stream output for documents up to 16 megabytes if:

      • document updates affect only a small fraction of the document structure or content, and

      • do not cause a replace change event. A replace event always includes the post-image.

  • To request a pre-image, you set fullDocumentBeforeChange to required or whenAvailable in db.collection.watch(). To request a post-image, you set fullDocument using the same method.

  • Pre-images are written to the config.system.preimages collection.

    • The config.system.preimages collection may become large. To limit the collection size, you can set expireAfterSeconds time for the pre-images as shown earlier.

    • Pre-images are removed asynchronously by a background process.

Important

Backward-Incompatible Feature

Starting in MongoDB 6.0, if you are using document pre- and post-images for change streams, you must disable changeStreamPreAndPostImages for each collection using the collMod command before you can downgrade to an earlier MongoDB version.

Tip

See also:

Specify Collation

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.

You can specify collation at the collection or view level. For example, the following operation creates a collection, specifying a collation for the collection (See Collation Document for descriptions of the collation fields):

db.createCollection( "myColl", { collation: { locale: "fr" } } );

This collation will be used by indexes and operations that support collation unless they explicitly specify a different collation. For example, insert the following documents into myColl:

{ _id: 1, category: "café" }
{ _id: 2, category: "cafe" }
{ _id: 3, category: "cafE" }

The following operation uses the collection's collation:

db.myColl.find().sort( { category: 1 } )

The operation returns documents in the following order:

{ "_id" : 2, "category" : "cafe" }
{ "_id" : 3, "category" : "cafE" }
{ "_id" : 1, "category" : "café" }

The same operation on a collection that uses simple binary collation (i.e. no specific collation set) returns documents in the following order:

{ "_id" : 3, "category" : "cafE" }
{ "_id" : 2, "category" : "cafe" }
{ "_id" : 1, "category" : "café" }

Tip

See also:

Create a View with Default Collation

Specify Storage Engine Options

You can specify collection-specific storage engine configuration options when you create a collection with db.createCollection(). Consider the following operation:

db.createCollection(
   "users",
   { storageEngine: { wiredTiger: { configString: "<option>=<setting>" } } }
)

This operation creates a new collection named users with a specific configuration string that MongoDB will pass to the wiredTiger storage engine. See the WiredTiger documentation of collection level options for specific wiredTiger options.

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db.commandHelp()