dropIndexes Event事件

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:BSON对象，用作更改流事件的标识符。在恢复更改流时，此值用作resumeAfter参数的resumeToken。_id对象具有以下形式：

{
   "_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. _data类型取决于MongoDB版本，在某些情况下，还取决于更改流打开或恢复时的功能兼容性版本（FCV）。See Resume Tokens for the full list of _data types.有关_data类型的完整列表，请参阅恢复令牌。

For an example of resuming a change stream by resumeToken, see Resume a Change Stream.有关通过resumeToken恢复更改流的示例，请参阅恢复更改流。

clusterTime is the timestamp from the oplog entry associated with the event.是与事件关联的oplog条目的时间戳。

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.由于oplog大小的限制，多文档事务可能会创建多个oplog条目。在事务中，给定oplog条目的变更流事件共享相同的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.具有相同clusterTime的事件可能并不都与同一事务相关。有些事件根本与事务无关。从MongoDB 8.0开始，这可能适用于任何部署上的事件。在以前的版本中，这种行为仅适用于分片集群上的事件。

To identify events for a single transaction, you can use the combination of lsid and txnNumber in the change stream event document.要识别单个事务的事件，可以在更改流事件文档中使用lsid和txnNumber的组合。

UUID identifying the collection where the change occurred.识别发生更改的集合。

The identifier for the session associated with the transaction.与事务关联的会话的标识符。

Only present if the operation is part of a multi-document transaction.仅当操作是多文档事务的一部分时才存在。

The namespace (database and or collection) affected by the event.受事件影响的命名空间（数据库和/或集合）。

The name of the database where the event occurred.发生事件的数据库的名称。

The name of the collection where the event occurred.发生事件的集合的名称。

Additional information on the change operation.有关更改操作的其他信息。

This document and its subfields only appears when the change stream uses expanded events.此文档及其子字段仅在更改流使用扩展事件时显示。

An array of documents listing the indexes that were dropped by the operation.列出操作删除的索引的文档数组。

The type of operation that the change notification reports.更改通知报告的操作类型。

Returns a value of dropIndexes for these change events.返回这些更改事件的dropIndexes值。

Together with the lsid, a number that helps uniquely identify a transction.与lsid一起，一个有助于唯一标识事务的数字。

Only present if the operation is part of a multi-document transaction.仅当操作是多文档事务的一部分时才存在。

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.数据库操作的服务器日期和时间。wallTime与clusterTime的不同之处在于，clusterTime是从与数据库操作事件关联的oplog条目中获取的时间戳。