Change Events

Change streams watch collections, databases, or deployments for changes.

When a change occurs on a watched resource, the change stream returns a change event notification document, with information on the operation and the changes it makes.

Operation Types

Event	Description
`create`	Occurs on the creation of a collection. Requires that you set the showExpandedEvents option to `true`. New in version 6.0.
`createIndexes`	Occurs on the creation of indexes on the collection. Requires that you set the showExpandedEvents option to `true`. New in version 6.0.
`delete`	Occurs when a document is removed from the collection.
`drop`	Occurs when a collection is dropped from a database.
`dropDatabase`	Occurs when a database is dropped.
`dropIndexes`	Occurs when an index is dropped from the collection. Requires that you set the showExpandedEvents option to `true`. New in version 6.0.
`insert`	Occurs when an operation adds documents to a collection.
`invalidate`	Occurs when an operation renders the change stream invalid.
`modify`	Occurs when a collection is modified. Requires that you set the showExpandedEvents option to `true`. New in version 6.0.
`refineCollectionShardKey`	Occurs when a shard key is modified. New in version 6.1.
`rename`	Occurs when a collection is renamed.
`replace`	Occurs when an update operation removes a document from a collection and replaces it with a new document.
`reshardCollection`	Occurs when the shard key for a collection and the distribution of data changes. Requires that you set the showExpandedEvents option to `true`. New in version 6.1: (Also available in 6.0.14)
`shardCollection`	Occurs when a collection is sharded. Requires that you set the showExpandedEvents option to `true`. New in version 6.0.
`update`	Occurs when an operation updates a document in a collection.

Note

The server might return update operations as replace events when the replace representation is more concise. If you listen for update operations, also listen for replace operations.

Resume Token

Each change event includes an _id field, which is a BSON object that serves as an identifier for the change stream event. For an example of resuming a change stream by resumeToken, see Resume a Change Stream.

Expanded Events

New in version 6.0.

Change streams support data definition language (DDL) event notifications, such as createIndexes and dropIndexes. To include expanded events, open a change stream cursor with the showExpandedEvents option.

For example:

let cur = db.names.aggregate( [ {
   $changeStream: {
       showExpandedEvents: true
     }
   }
 ] )
cur.next()

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