PREMIUM EDITION FEATUREThis is a Premium Edition feature. All Premium Edition features are available out of the box without additional cost on RisingWave Cloud. For self-hosted deployments, users need to purchase a license key to access this feature. To purchase a license key, please contact sales team at sales@risingwave-labs.com.For a full list of Premium Edition features, see RisingWave Premium Edition.

​
Prerequisites

Time travel requires the meta store type to be SQL-compatible. We recommend reserving at least 50 GB of disk space for the meta store. The system parameter time_travel_retention_ms controls time travel functionality. By default, it’s set to 600000, i.e. 10 minutes. To modify retention period, you need to alter this system parameter to a non-zero value. For example, you can set time_travel_retention_ms to 86400000 (1 day). Then historical data older than this period will be deleted and no longer accessible.
Increasing time travel retention period will introduce additional overhead to both the meta store and the object store.

​
Syntax

Specify FOR SYSTEM_TIME AS OF separately for each table accessing historical data. The following subclauses can be used:
  • Unix timestamp in seconds. For example, SELECT * FROM t_foo FOR SYSTEM_TIME AS OF 1721024455;.
  • Datetime. For example, SELECT * FROM t_foo FOR SYSTEM_TIME AS OF '2000-02-29T12:13:14-08:30';.
  • NOW() [ - Interval ]. For example, SELECT * FROM t_foo FOR SYSTEM_TIME AS OF NOW() - '10' SECOND;.
If you specify a point in time that is outside the time travel period, the query will return an error, like time travel: version not found for epoch.

​
Storage space reclamation

Stale time travel data in both the meta and object stores is automatically removed in the background, freeing up storage space.