Database Manual / Change Streams / Change Events

drop Event

Synopsis

drop: A drop event occurs when a collection is dropped from a database.

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	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.
`operationType`	string	The type of operation that the change notification reports. Returns a value of `drop` 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 illustrates a drop event:

{
   "_id": { <Resume Token> },
   "operationType": "drop",
   "clusterTime": <Timestamp>,
   "wallTime": <ISODate>,
   "ns": {
      "db": "engineering",
      "coll": "users"
   }
}

A drop event leads to an invalidate event for change streams opened against its own ns collection.

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