Time Series Collection Limitations时间序列采集限制

Unsupported Features不支持的功能

The following features are not supported for time series collections:时间序列集合不支持以下功能：

• Atlas SearchAtlas搜索
• Change streams更改流
• Client-Side Field Level Encryption客户端字段级加密
• Database Triggers数据库触发器
• GraphQL APIGraphQL API
• Schema validation rules架构验证规则
• reIndex
• renameCollection

Atlas Device Sync is only supported if the time series collections are asymmetrically synchronized. 仅当时间序列集合不对称同步时才支持。For details, see Enable Atlas Device Sync.有关详细信息，请参阅启用Atlas设备同步。

Aggregation $merge聚合$merge

You cannot use the $merge aggregation stage to add data from another collection to a time series collection.不能使用$merge聚合阶段将其他集合中的数据添加到时间序列集合中。

Deletes删除

Starting in MongoDB 5.1, you can perform limited delete operations on time series collections. MongoDB 7.0 removes most limitations from operations that are based on the delete command.从MongoDB 5.1开始，您可以对时间序列集合执行有限的删除操作。MongoDB 7.0消除了基于delete命令的操作的大多数限制。

Time series deletes are not supported for multi-document transactions.多文档事务处理不支持时间序列删除。

From MongoDB 5.1 to 6.3, delete commands must meet the following requirements:从MongoDB 5.1到6.3，delete命令必须满足以下要求：

• You can only match on metaField field values.只能在metaField字段值上匹配。
• Your delete command must not limit the number of documents to be deleted. Set justOne: false or use the deleteMany() method.删除命令不得限制要删除的文档数。设置justOne: false或使用deleteMany()方法。

Starting in MongoDB 7.0, there is only one time series related limitation on these delete commands:从MongoDB 7.0开始，这些delete命令只有一个与时间序列相关的限制：

• delete
• deleteOne()
• deleteMany()
• Bulk.find.delete()
• Bulk.find.deleteOne()

You cannot use these commands with multi-document transactions. There are no other restrictions.不能将这些命令用于多文档事务。没有其他限制。

If a time series collection contains documents with timeField timestamps before 1970-01-01T00:00:00.000Z or after 2038-01-19T03:14:07.000Z, no documents are deleted from the collection by the TTL "time to live" feature.如果时间序列集合包含timeField时间戳在1970-01-01T00:00:00.000Z之前或2038-01-19T03:14:07.000Z之后的文档，则TTL“生存时间”功能不会从集合中删除任何文档。

For details on TTL deletes, see Expire Data from Collections by Setting TTL.有关TTL删除的详细信息，请参阅通过设置TTL使集合中的数据过期。

Updates更新

Starting in MongoDB 5.1, you can perform limited update operations.从MongoDB 5.1开始，您可以执行有限的更新操作。

Update commands must meet the following requirements:更新命令必须满足以下要求：

• You can only match on the metaField field value.只能在metaField字段值上匹配。
• You can only modify the metaField field value.您只能修改metaField字段值。
• Your update document can only contain update operator expressions.更新文档只能包含更新运算符表达式。
• Your update command must not limit the number of documents to be updated. 更新命令不得限制要更新的文档数。Set multi: true or use the updateMany() method.设置multi:true或使用updateMany()方法。
• Your update command must not set upsert: true.您的更新命令不得设置upsert: true。

In MongoDB 5.0, time series collections only support insert operations and read queries. Updates and manual delete operations result in an error.在MongoDB 5.0中，时间序列集合只支持插入操作和读取查询。更新和手动删除操作会导致错误。

To automatically delete old data, set up automatic removal (TTL).要自动删除旧数据，请设置自动删除（TTL）。

To remove all documents from a collection, use the drop() method to drop the collection.若要从集合中删除所有文档，请使用drop()方法删除集合。

Time Series Secondary Indexes时间序列辅助索引

MongoDB 6.0 and later features improved support for secondary indexes on time series collections. MongoDB 6.0及更高版本的功能改进了对时间序列集合的辅助索引的支持。For a summary of these options, see Time Series Secondary Indexes in MongoDB 6.0 and Later.有关这些选项的摘要，请参阅MongoDB 6.0及更高版本中的时间序列辅助索引。

Capped Collections封顶集合

You cannot create a time series collection as a capped collection.不能将时间序列集合创建为封顶集合。

Modification of Collection Type修改集合类型

You can only set the collection type when you create a collection:您只能在创建集合时设置集合类型：

• An existing collection cannot be converted into a time series collection.无法将现有集合转换为时间序列集合。
• A time series collection cannot be converted into a different collection type.时间序列集合无法转换为其他集合类型。

To move data from an existing collection to a time series collection, migrate data into a time series collection.要将数据从现有集合移动到时间序列集合，请将数据迁移到时间序列集中。

Modification of timeField and metaFieldtimeField和metaField的修改

You can only set a collection's timeField and metaField parameters when you create the collection. You cannot modify these parameters later.创建集合时，只能设置集合的timeField和metaField参数。以后不能修改这些参数。

Modifying Bucket Parameters修改桶参数

Once you set a collection's granularity or custom bucketing parameters bucketMaxSpanSeconds and bucketRoundingSeconds, you can increase them, but not decrease them. 设置集合的granularity或自定义bucketMaxSpanSeconds和bucketRoundingSeconds参数后，可以增加它们，但不能减少它们。Use the collMod command to modify the parameters. 使用collMod命令可以修改参数。For example:例如：

db.runCommand({
   collMod: "timeseries",
   timeseries: { bucketMaxSpanSeconds: 3600, bucketRoundingSeconds: 3600 }
})

Sharding分片

Starting in MongoDB 5.1 (and 5.0.6), you can create sharded time series collections.从MongoDB 5.1（和5.0.6）开始，您可以创建分片的时间序列集合。

In versions earlier than MongoDB 5.0.6, you cannot shard time series collections.在MongoDB 5.0.6之前的版本中，不能对时间序列集合进行分片。

Transactions事务

You cannot write to time series collections in transactions.不能写入事务中的时间序列集合。

Views视图

• Time series collections are writable non-materialized views. Limitations for views apply to time series collections.时间序列集合是可写的非物化视图。视图的限制适用于时间序列集合。
• You cannot create a view from a time series bucket collection namespace (namely, a collection prefixed with system.buckets).不能从时间序列桶集合命名空间（即以system.buckets为前缀的集合）创建视图。