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Retention Policies for System Relations ​

Some system relations can grow in space with time, because of the number of queries being run, sessions being opened, etc. We provide a retention mechanism for some of these relations:

  • Removing all records older than a given age.
  • Removing the oldest records when the relation takes more than a given amount of space in the storage.

Interface ​

The current retention configuration can be observed in sys.retention.

The retention history is stored in sys.log_retention.

To modify the retention configuration for a given relation, an ALTER TABLE statement needs to be run, for example:

sql
ALTER TABLE <relation> SET RETENTION_SIZE <size>

See ALTER TABLE for the complete SQL syntax.

Notes ​

  • The retention process will trigger every hour.
  • When removing records because of space limit, no record younger than a day will be removed.
  • The retention policy configuration does not survive upgrades and will need to be re-applied.

Default configuration ​

By default, the following retention policies are set up:

RelationAge RetentionSize RetentionMinimum Age RetentionMinimum Size Retention
sys.log_analyze3 months1GB1 day128MB
sys.log_authenticationDisabledDisabled1 day128MB
sys.log_backup3 months1GB1 day128MB
sys.log_cluster_event3 months1GB1 day128MB
sys.log_load3 months1GB1 day128MB
sys.log_query1 month32GB1 day1GB
sys.log_query_analyze1 month32GB1 day128MB
sys.log_query_usage1 month32GB1 day128MB
sys.log_restore3 months1GB1 day128MB
sys.log_replica_status3 months1GB1 day128MB
sys.log_retention3 months1GB1 day128MB
sys.log_sessionDisabledDisabled1 day128MB
sys.log_unload3 months1GB1 day128MB