mongodbmysqlbinlogchangestreammongodb-oplog

MongoDB Change Stream: Can I get value before update/delete?


Change Stream Event on an update operation just return the document that changes to, same as oplog. Can I get the document (or some updated values) before update?

MySQL row-based binlog can do this with full binlog_row_image.


Solution

  • No, from change stream an update event looks like:

    {
       _id: { < Resume Token > },
       operationType: 'update',
       clusterTime: <Timestamp>,
       ns: {
          db: 'engineering',
          coll: 'users'
       },
       documentKey: {
          _id: ObjectId("58a4eb4a30c75625e00d2820")
       },
       updateDescription: {
          updatedFields: {
             email: 'alice@10gen.com'
          },
          removedFields: ['phoneNumber']
       }
    }
    

    Only the new values are present, unlike MySQL where you get both after and before.