db.createCollection()

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.

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.

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.

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.

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.

Starting in MongoDB 5.3, you can create a collection with a clustered index. Clustered indexes are stored in the same WiredTiger file as the collection. The resulting collection is called a clustered collection.

The clusteredIndex field has the following syntax:

clusteredIndex: {
   key: <object>,
   unique: <boolean>,
   name: <string>
}

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.

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>
}

To enable change stream pre- and post-images for the collection, set enabled to true.

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.

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.

Starting in MongoDB 7.2, you can't specify wiredTiger storage engine encryption options when you create a collection with db.createCollection(). To configure encryption for the WiredTiger storage engine, see Encryption at Rest.

For details, see Specify Storage Engine Options.

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.

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

"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.

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.

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.

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.

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".