IcebergTableMaintainer expireSnapshots keep one snapshot

[lurnagao-dahua]

Hi, expireSnapshots iceberg table in IcebergTableMaintainer.
table .expireSnapshots() .retainLast(1) .expireOlderThan(olderThan)
Why only keep one snapshot and not support configurable？

[zhoujinsong]

Hi,

Method retainLast helps to keep at least N snapshots even if they are older than the expiration timestamp[1].
Amoro lets users configure the expiration time by table property:change.data.ttl.minutes[2].

I'm not sure if you're asking want to support retaining more snapshots when expiration time is configured.

references:
[1] https://github.com/apache/iceberg/blob/main/api/src/main/java/org/apache/iceberg/ExpireSnapshots.java#L72
[2] https://amoro.apache.org/docs/latest/configurations/#data-cleaning-configurations

[lurnagao-dahua]

Hi,I want to support retaining more snapshots when expiration time is configured.

[zhoujinsong]

Could you provide some specific scenarios to help us understand why you need additional configurations?

[lurnagao-dahua]

Iceberg parameter history.expire.min-snapshots-to-keep ,default min number of snapshots to keep on the table and all of its branches while expiring snapshots.
We may use this parameter to allow the user to determine the number of snapshots to be retained