Database Manual / Change Streams / Change Events

create Event

Summary

create

New in version 6.0.

A create event occurs when a collection is created on a watched database and the change stream has the showExpandedEvents option set to true.

Description

FieldTypeDescription

_id

Document

A BSON object which serves as an identifier for the change stream event. This value is used as the resumeToken for the resumeAfter parameter when resuming a change stream. The _id object has the following form:

{
   "_data" : <BinData|hex string>
}

The _data type depends on the MongoDB versions and, in some cases, the feature compatibility version (FCV) at the time of the change stream's opening or resumption. See Resume Tokens for the full list of _data types.

For an example of resuming a change stream by resumeToken, see Resume a Change Stream.

clusterTime

Timestamp

clusterTime is the timestamp from the oplog entry associated with the event.

Due to oplog size limits, multi-document transactions may create multiple oplog entries. In a transaction, change stream events staged in a given oplog entry share the same clusterTime.

Events with the same clusterTime may not all relate to the same transaction. Some events don't relate to a transaction at all. Starting in MongoDB 8.0, this may be true for events on any deployment. In previous versions, this behavior was possible only for events on a sharded cluster.

To identify events for a single transaction, you can use the combination of lsid and txnNumber in the change stream event document.

Changed in version 8.0.

collectionUUID

UUID

If the change occurred on a collection, collectionUUID indicates the collection's UUID. If the change occurred on a view, collectionUUID doesn't exist.

New in version 6.0.

lsid

document

The identifier for the session associated with the transaction.

Only present if the operation is part of a multi-document transaction.

ns

document

The namespace (database and or collection) affected by the event.

ns.coll

string

The name of the collection where the event occurred.

ns.db

string

The name of the database where the event occurred.

nsType

string

Shows the namespace type of the collection created by this event.

"collection"
Indicates the event creates a collection.
"timeseries"
Indicates the event creates a timeseries collection.
"view"
Indicates the event creates a non-timeseries view.

New in version 8.1: (also available in 8.0.5).

operationDescription

document

Additional information on the change operation.

This document and its subfields only appears when the change stream uses expanded events.

New in version 6.0.

operationDescription.
idIndex

document

The default _id index for a new collection.

New in version 6.0.

operationType

string

The type of operation that the change notification reports.

Returns a value of create for these change events.

txnNumber

NumberLong

Together with the lsid, a number that helps uniquely identify a transction.

Only present if the operation is part of a multi-document transaction.

wallTime

ISODate

The server date and time of the database operation. wallTime differs from clusterTime in that clusterTime is a timestamp taken from the oplog entry associated with the database operation event.

New in version 6.0.

Example

The following example shows a create event:

{
   "_id": { <ResumeToken> },
   "operationType": "create",
   "clusterTime": Timestamp({ t: 1654894547, i: 24 }),
   "collectionUUID": UUID("98046a1a-b649-4e5b-9c75-67594221ce19"),
   "wallTime": ISODate("2022-06-10T20:55:47.947Z"),
   "ns": {
      "db": "test",
      "coll": "names"
   },
   "operationDescription": {
      "idIndex": { "v": 2, "key": { _id: 1 }, "name": "_id_" }
   }
}