[CASSANDRA-18102] Add a virtual table to list snapshots

[Paulo Motta]

Hi,

I wanted to give a heads up that we're adding a new virtual table
on CASSANDRA-18102[1] to query snapshots.

This is similar to the nodetool listsnapshots command but give more
flexibility to users by allowing querying snapshots by
keyspace/size/creation date, for example:

###
cqlsh> SELECT * from system_views.snapshots WHERE keyspace_name = 'ks1' AND
true_size > 1080;

 name | keyspace_name | table_name | created_at  |
ephemeral | expires_at  | size_on_disk | true_size
--+---++-+---+-+--+---
  ks1 |   ks1 | t1 | 2023-03-19 17:24:39.236000+ |
False | 2023-03-20 03:24:39.236000+ | 6186 |  1082
  ks1 |   ks1 | t2 | 2023-03-19 17:24:39.236000+ |
False | 2023-03-20 03:24:39.236000+ | 6186 |  1082

(2 rows)
###

One limitation is that each query will traverse data directories to look
for snapshots, which can be inefficient, but we plan to address this before
releasing this on 5.0 by caching snapshot metadata in memory on
CASSANDRA-18111[2].

Let me know if you have any feedback or concerns.

Thanks,

Paulo

[1] - https://issues.apache.org/jira/browse/CASSANDRA-18102
[2] - https://issues.apache.org/jira/browse/CASSANDRA-18111

Re: [DISCUSS] Drop support for sstable formats m* (in trunk)

[Brandon Williams]

On Fri, Mar 17, 2023 at 2:38 PM Mick Semb Wever  wrote:
> So is there appetite for such a patch to fail or warn (guardrail?) to prevent 
> a node running on a new version that does not support sstable formats 
> existing on other nodes?

I think this makes sense, whatever the mechanism.