Time Series Collection Limitations

Unsupported Features

The following features are not supported for time series collections.

• Client-side field level encryption

• reIndex

• Change streams

• Database Triggers

• GraphQL API

• Atlas Search

• Realm Sync

• Data API

• Schema validation rules

Constraints

The maximum size of a measurement document is 4 MB.

Aggregation $out and $merge

You can't use aggregation pipeline stages $out and $merge to output or merge into to time series collections from another collection.

Updates and Deletes

Starting in MongoDB 5.1, you can perform some delete and update operations.

Delete commands must meet the following requirements:

• The query may only match on metaField field values.

• The delete command may not limit the number of documents to be deleted. You must use a delete command with justOne: false or the deleteMany() method.

Update commands must meet the following requirements:

• The query may only match on metaField field values.

• The update command may only modify the metaField field value.

• The update must be performed with an update document that contains only update operator expressions.

• The update command may not limit the number of documents to be updated. You must use an update command with multi: true or the updateMany() method.

• The update command may not set 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.

To automatically delete old data, set up automatic removal (TTL).

To remove all documents from a collection, use the drop() method to drop the collection.

Secondary Indexes

You can add secondary indexes on the fields specified as the timeField and the metaField. If the field value for the metaField field is a document, you can also create secondary indexes on fields inside that document.

In MongoDB 5.1, the metaField doesn't support text indexes.

In MongoDB 5.0, the metaField doesn't support the following index types:

• 2d

• 2dsphere

• text

Secondary indexes don't support the following index properties:

• TTL

• Unique

• Partial

Capped Collections

A time series collection can't be created as a capped collection.

Modification of Collection Type

A collection's type can only be set when creating the collection:

• An existing collection can't be converted into a time series collection.

• A time series collection can't be converted into a different collection type.

To move data from an existing collection to a time series collection, migrate data into a time series collection.

Modification of timeField and metaField

You can only set a collection's timeField and metaField parameters when creating the collection. After creation these parameters can't be modified.

Modification of granularity

Once the granularity is set it can only be increased by one level at a time. From "seconds" to "minutes" or from "minutes" to "hours". Other changes are not allowed. If you need to change the granularity from "seconds" to "hours", first increase the granularity to "minutes" and then to "hours".

Sharding

Starting in MongoDB 5.1 (and 5.0.6), sharded time series collections are supported. When using sharded time series collections, you cannot modify the granularity of a sharded time series collection.

In versions earlier than MongoDB 5.0.6, you cannot shard time series collections.

Transactions

You can't write to time series collections in transactions.