When the expiration_log is enabled than log shards that are older than the provided value will be dropped. This setting should be an integer value with the time precision of the database.
By default this setting is disabled.
# Suppose we have a second precision database,
# then this will drop log shards, older than 4 weeks
alter database set expiration_log 3600*24*7*4
# Disable shard expiration:
alter database set expiration_log 0
After setting the expiration_log that results in more shards being dropped than the drop_threshold allows, an error is displayed and set ignore_threshold true may be added to ignore this warning.
alter database set expiration_log 52w set ignore_threshold true