db.createCollection()¶

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Definition
Examples

Definition¶

db.createCollection(name, options)¶

Creates a new collection explicitly.

Because MongoDB creates a collection implicitly when the collection is first referenced in a command, this method is used primarily for creating new capped collections.

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

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

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db.createCollection(<name>, { capped: <boolean>,
                              autoIndexId: <boolean>,
                              size: <number>,
                              max: <number>,
                              storageEngine: <document> } )

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

Parameter	Type	Description
`name`	string	The name of the collection to create.
`options`	document	Optional. Configuration options for creating a capped collection or for preallocating space in a new collection.

The options document creates a capped collection or preallocates space in a new ordinary collection. 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.
`autoIndexId`	boolean	Optional. Specify `false` to disable the automatic creation of an index on the `_id` field. Important For replica sets, all collections must have `autoIndexId` set to `true`.
`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.
`usePowerOf2Sizes`	boolean	Optional. Available for the MMAPv1 storage engine only. Deprecated since version 3.0: For the MMAPv1 storage engine, all collections use the power of 2 sizes allocation unless the `noPadding` option is `true`. The `usePowerOf2Sizes` option does not affect the allocation strategy.
`noPadding`	boolean	Optional. Available for the MMAPv1 storage engine only. New in version 3.0: `noPadding` flag disables the power of 2 sizes allocation for the collection. With `noPadding` flag set to true, the allocation strategy does not include additional space to accommodate document growth, as such, document growth will result in new allocation. Use for collections with workloads that are insert-only or in-place updates (such as incrementing counters). Defaults to `false`. Warning Do not set `noPadding` if the workload includes removes or any updates that may cause documents to grow. For more information, see No Padding Allocation Strategy.
`storageEngine`	document	Optional. Available for the WiredTiger storage engine only. New in version 3.0. 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: copy { <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.

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:

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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.

Specify Storage Engine Options¶

New in version 3.0.

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

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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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