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Change Events

dropDatabase

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  • Synopsis
  • Description
  • Example

Synopsis

dropDatabase

A dropDatabase event occurs when a database is dropped.

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.

On sharded clusters, events with the same clusterTime may not all relate to the same transaction. Some events don't relate to a transaction at all.

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

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.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 dropDatabase 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.

Example

The following example illustrates a dropDatabase event:

{
   "_id": { <Resume Token> },
   "operationType": "dropDatabase",
   "clusterTime": <Timestamp>,
   "ns": {
      "db": "engineering"
   }
}

A dropDatabase command generates a drop event for each collection in the database before generating a dropDatabase event for the database.

A dropDatabase event leads to an invalidate event for change streams opened against its own ns.db database.

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