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From Duncan Sands <>
Subject Re: Deleted columns reappear after "repair"
Date Tue, 24 Mar 2015 17:39:49 GMT
Hi Roman,

On 24/03/15 18:05, Roman Tkachenko wrote:
> Hi Duncan,
> Thanks for the response!
> I can try increasing gc_grace_seconds and run repair on all nodes. It does not
> make sense though why all *new* deletes (for the same column that resurrects
> after repair) I do are forgotten as well after repair? Doesn't Cassandra insert
> a new tombstone every time delete happens?

it does.  Maybe the data you are trying to delete has a timestamp (writetime) in 
the future, for example because clocks aren't synchronized between your nodes.

> Also, how do I find out the value to set gc_grace_seconds to?

It needs to be big enough that you are sure to repair your entire cluster in 
less than that time.  For example, observe how long repairing the entire cluster 
takes and multiply by 3 or 4 (in case a repair fails or is interrupted one day).

Once incremental repair is solid maybe the whole gc_grace thing will eventually 
go away, eg by modifying C* to only drop known repaired tombstones.

Ciao, Duncan.

> Thanks.
> On Tue, Mar 24, 2015 at 9:38 AM, Duncan Sands <
> <>> wrote:
>     Hi Roman,
>     On 24/03/15 17:32, Roman Tkachenko wrote:
>         Hey guys,
>         Has anyone seen anything like this behavior or has an explanation for it? If
>         not, I think I'm gonna file a bug report.
>     this can happen if repair is run after the tombstone gc_grace_period has
>     expired.  I suggest you increase gc_grace_period.
>     Ciao, Duncan.

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