Deleting counters

[Robert Wille <rw...@fold3.com>]

At the Cassandra Summit I became aware of that there are issues with deleting counters. I have a few questions about that. What is the bad thing that happens (or can possibly happen) when a counter is deleted? Is it safe to delete an entire row of counters? Is there any 2.0.x version of Cassandra in which it is safe to delete counters? Is there an access pattern in which it is safe to delete counters in 2.0.x?

Thanks

Robert

Re: Deleting counters

[Robert Coli <rc...@eventbrite.com>]

On Thu, Oct 9, 2014 at 3:29 PM, Robert Wille <rw...@fold3.com> wrote:

> What is the bad thing that happens (or can possibly happen) when a counter
> is deleted?
>

You get totally wacky counter state if you, later, re-create and use it.

https://issues.apache.org/jira/browse/CASSANDRA-6532
and
https://issues.apache.org/jira/browse/CASSANDRA-7346

Have some good discussion.

Is it safe to delete an entire row of counters?


Not unless :
a) you will never use that particular counter row again
OR
b) gc_grace_seconds has passed and you have repaired and run a major
compaction on every node, such that 100% of such tombstones have been
removed


> Is there any 2.0.x version of Cassandra in which it is safe to delete
> counters?


See above, 2.0 is the same as any other version for this behavior.

Is there an access pattern in which it is safe to delete counters in 2.0.x?
>

The summary of the above is that, in practice, it is only safe to delete
counters if you plan to never use that particular counter row again.

=Rob