Navigation

Time Series Collection Limitations

On this page

This page describes limitations of time series collections.

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.

Time Series 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:

Secondary indexes don’t support the following index properties:

For improvements to time series secondary indexes available starting in MongoDB 6.0, see Time Series Secondary Indexes in MongoDB 6.0.

If there are secondary indexes on time series collections and you need to downgrade the Feature Compatibility Version (FCV), you must first drop any secondary indexes that are incompatible with the downgraded FCV. See setFeatureCompatibilityVersion.

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:

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.

Sharding Administration Commands

Starting in MongoDB 5.2 (and 5.1.2, 5.0.6), you can run sharding administration commands (such as moveChunk) on the system.buckets collection.

In versions earlier than MongoDB 5.0.6, you cannot run sharding administration commands for sharded time series collections.

Shard Zones

MongoDB does not support creating zones for sharded time series collections.

Shard Keys

When sharding time series collections, you can only specify the following fields in the shard key:

  • The metaField
  • Sub-fields of metaField
  • The timeField

You may specify combinations of these fields in the shard key. No other fields, including _id, are allowed in the shard key pattern.

When you specify the shard key:

Tip

Avoid specifying only the timeField as the shard key. Since the timeField increases monotonically, it may result in all writes appearing on a single chunk within the cluster. Ideally, data is evenly distributed across chunks.

To learn how to best choose a shard key, see:

Transactions

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

Note

Reads from time series collections are supported in transactions.

© MongoDB, Inc 2008-present. MongoDB, Mongo, and the leaf logo are registered trademarks of MongoDB, Inc.