2i indexes and keys request inconsistencies

Russell Brown russell.brown at me.com
Wed Mar 9 05:49:49 EST 2016


I wonder if you have some keys that are hanging around on one of the N partitions but are deleted elsewhere (and the tombstones reaped?). 2i uses coverage which is essentially r=1 on a covering set of vnodes. But you think read-repair/AAE would bring convergence, so it is perplexing. I wonder if we can get a look at the “phantom” keys. Either via r=1 GET or some attach to console, get directly from the backend magic.


On 9 Mar 2016, at 09:06, Alexander Popov <mogadanez at gmail.com> wrote:

> @Matthew 
> 
> No, db activity was very low at this time, and keys returned by this queries  was deleted long time ago ( some of them at Dec 2015 )
> 
> I got this  issue when proceed maintenance task  which touch all keys in DB, list all keys by /keys?keys=true query, read, upgrade, save.
> 
> We have some logic depends on 2i indexes results -  ( count number of related   keys ). But if it returns phantom keys,
>  I cannot trust this data, need to double check by getting each object, but this is more expensive operation
> 
> 
> 
> 
> On Tue, Mar 8, 2016 at 10:21 PM, Matthew Von-Maszewski <matthewv at basho.com> wrote:
> Is the database being actively modified during your queries?  
> 
> Queries can lock down a "snapshot" within leveldb.  The query operation can return keys that existed at the time of the snapshot, but have been subsequently deleted by normal operations.
> 
> In such a case, the query is correct in giving you the key and the 404 afterward is also correct.  They represent two different versions of the database over time.
> 
> Not sure if this is a valid scenario for you or not.
> 
> Matthew
> 
> 
>> On Mar 8, 2016, at 1:22 PM, Alexander Popov <mogadanez at gmail.com> wrote:
>> 
>> Noticied that sometimes 2i query and all keys requesrs returns extra records ~2% of all records.
>> 
>> When call this items by get request after,  it returns 404 and after that key stops to returns in 2i and keys requests.
>> 
>> Does it normally or my database is corrupted?
>> 
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