Database Manual / Change Streams / Change Events

insert Event

Summary

insert: An insert event occurs when an operation adds documents to a collection.

Description

Field	Type	Description
`_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	UUID identifying the collection where the change occurred. New in version 6.0. The `collectionUUID` field is only included if the change stream is created with the `showExpandedEvents` field set to `true`. For details, see showExpandedEvents.
`documentKey`	document	Document that contains the `_id` value of the document created or modified by the CRUD operation. For sharded collections, this field also displays the full shard key for the document. The `_id` field is not repeated if it is already a part of the shard key.
`fullDocument`	document	The document created by the operation. Changed in version 6.0. Starting in MongoDB 6.0, if you set the `changeStreamPreAndPostImages` option using `db.createCollection()`, `create`, or `collMod`, then the `fullDocument` field shows the document after it was inserted, replaced, or updated (the document post-image). `fullDocument` is always included for `insert` events.
`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.
`operationType`	string	The type of operation that the change notification reports. Returns a value of `insert` 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.

Behavior

Update Operations

The update command can produce different change events (not just update) depending on the actual changes it makes to the collection.

Change Event	Description
`update`	The update operation modified an existing document.
`replace`	The update operation replaced the document or produced a diff that was more verbose than the original document, causing MongoDB to replace it.
`insert`	The update operation attempted to update a document that doesn't exist and instead added the document to the collection. This only occurs when the update runs with the `upsert` option enabled.

Example

The following example illustrates an insert event:

{
   "_id": { <Resume Token> },
   "operationType": "insert",
   "clusterTime": <Timestamp>,
   "wallTime": <ISODate>,
   "ns": {
      "db": "engineering",
      "coll": "users"
   },
   "documentKey": {
      "userName": "alice123",
      "_id": ObjectId("599af247bb69cd89961c986d")
   },
   "fullDocument": {
      "_id": ObjectId("599af247bb69cd89961c986d"),
      "userName": "alice123",
      "name": "Alice"
   }
}

The documentKey field includes both the _id and the userName field. This indicates that the engineering.users collection is sharded, with a shard key on userName and _id.

The fullDocument document represents the version of the document at the time of the insert.

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