create¶

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Definition
Example

Definition¶

create¶

Explicitly creates a collection. create has the following form:

{ create: <collection_name>,
  capped: <true|false>,
  autoIndexId: <true|false>,
  size: <max_size>,
  max: <max_documents>
}

create has the following fields:

Field	Type	Description
`create`	string	The name of the new collection.
`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. Before 2.2, the default value for `autoIndexId` was `false`.
`size`	integer	Optional. The maximum size for the capped collection. Once a capped collection reaches its maximum size, MongoDB overwrites older old documents with new documents. The `size` field is required for capped collections.
`max`	integer	Optional. The maximum number of documents to keep in the capped collection. The `size` limit takes precedence over this limit. If a capped collection reaches its maximum size before it reaches the maximum number of documents, MongoDB removes old documents. If you use this limit, ensure that the `size` limit is sufficient to contain the documents limit.

For more information on the autoIndexId field in versions before 2.2, see _id Fields and Indexes on Capped Collections.

The db.createCollection() method wraps the create command.

Note

The create command obtains a write lock on the affected database and will block other operations until it has completed. The write lock for this operation is typically short lived. However, allocations for large capped collections may take longer.

Example¶

To create a capped collection limited to 64 kilobytes, issue the command in the following form:

copy

db.runCommand( { create: "collection", capped: true, size: 64 * 1024 } )

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