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shardCollection Event

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Summary摘要

shardCollection

New in version 6.0. 6.0版新增。

A shardCollection event occurs when a collection is sharded.对集合进行分片时，会发生shardCollection事件。

Description描述

Field字段Type类型Description描述
_idDocumentA BSON object which serves as an identifier for the change stream event. BSON对象，用作更改流事件的标识符。This value is used as the resumeToken for the resumeAfter parameter when resuming a change stream. 恢复更改流时，此值用作resumeAfter参数的resumeToken。The _id object has the following form: _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.请参阅恢复令牌以获取_data类型的完整列表。
For an example of resuming a change stream by resumeToken, see Resume a Change Stream.
clusterTimeTimestampThe timestamp from the oplog entry associated with the event.
Change stream event notifications associated with a multi-document transaction all have the same clusterTime value: the time when the transaction was committed.
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.
New in version 4.0. 4.0版新增。
collectionUUIDUUIDUUID identifying the collection where the change occurred.
New in version 6.0. 6.0版新增。
lsiddocumentThe identifier for the session associated with the transaction.
Only present if the operation is part of a multi-document transaction.
New in version 4.0. 4.0版新增。
nsdocumentThe namespace (database and or collection) affected by the event.
ns.collstringThe name of the collection where the event occurred.
ns.dbstringThe name of the database where the event occurred.
operationDescriptiondocumentAdditional information on the change operation.
This document and its subfields only appears when the change stream uses expanded events.
New in version 6.0. 6.0版新增。
operationDescription.
numInitialChunks		longNumber of chunks created on each shard during a shardCollection operation.
New in version 6.0. 6.0版新增。
operationDescription.
presplitHashedZones		booleanIndicates whether the shard chunks were pre-split according to zones when the collection becamed sharded.
New in version 6.0. 6.0版新增。
operationDescription.
shardKey		documentThe shard key for the collection where the change occurred.
New in version 6.0. 6.0版新增。
operationDescription.
unique		booleanThis has a value of true if the collection was sharded with a unique shard key.
New in version 6.0. 6.0版新增。
operationTypestringThe type of operation that the change notification reports.
Returns a value of shardCollection for these change events.
txnNumberNumberLongTogether with the lsid, a number that helps uniquely identify a transction.
Only present if the operation is part of a multi-document transaction.
New in version 4.0. 4.0版新增。
wallTimeISODateThe 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. 6.0版新增。

Example实例

The following example shows a shardCollection event:

{
   "_id": { <ResumeToken> },
   "operationType": "shardCollection",
   "clusterTime": Timestamp({ t: 1654894852, i: 52 }),
   "collectionUUID": UUID("98046a1a-b649-4e5b-9c75-67594221ce19"),
   "wallTime": ISODate("2022-06-10T21:00:52.854Z"),
   "ns": {
      "db": "test",
      "coll": "authors"
   },
   "operationDescription": {
      "shardKey": { "age": "hashed" },
      "unique": false,
      "numInitialChunks": Long("0"),
      "presplitHashedZones": false
   }
}