cloneCollectionAsCapped

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Definition

Compatibility
Syntax
Behavior

Definition

cloneCollectionAsCapped: The cloneCollectionAsCapped command creates a new capped collection from an existing, non-capped collection within the same database. The operation does not affect the original non-capped collection.

Compatibility

This command is available in deployments hosted in the following environments:

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

Important

This command is not supported in M0, M2, and M5 clusters or in serverless instances. For more information, see Unsupported Commands.

MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Syntax

The command has the following syntax:

{ cloneCollectionAsCapped: <existing collection>,
  toCollection: <capped collection>,
  size: <capped size>,
  writeConcern: <document>,
  comment: <any>
}

Command Fields

The command takes the following fields:

Field	Description
cloneCollectionAsCapped	The name of the existing collection to copy.
toCollection	The name of the new capped collection to create. The name of the new capped collection must be distinct and cannot be the same as that of the original existing collection.
size	The maximum size,in bytes, for the capped collection.
writeConcern	Optional. A document expressing the write concern of the `drop` command. Omit to use the default write concern.
`comment`	Optional. A user-provided comment to attach to this command. Once set, this comment appears alongside records of this command in the following locations: mongod log messages, in the `attr.command.cursor.comment` field. Database profiler output, in the `command.comment` field. `currentOp` output, in the `command.comment` field. A comment can be any valid BSON type (string, integer, object, array, etc).

The command copies an existing collection and creates a new capped collection with a maximum size specified by the capped size in bytes.

To replace the original non-capped collection with a capped collection, use the convertToCapped command.

Behavior

If the capped size is less than the size of the source collection, then not all documents in the source collection will exist in the destination capped collection.

This holds a database exclusive lock for the duration of the operation. Other operations which lock the same database will be blocked until the operation completes. See What locks are taken by some common client operations? for operations that lock the database.

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