[jira] [Updated] (CASSANDRA-2800) OPP#describeOwnership reports incorrect ownership

["Jon Hermes (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-2800?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jon Hermes updated CASSANDRA-2800:
----------------------------------

    Attachment: 2800.txt

> OPP#describeOwnership reports incorrect ownership
> -------------------------------------------------
>
>                 Key: CASSANDRA-2800
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2800
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 0.7.4
>            Reporter: Jon Hermes
>            Assignee: Jon Hermes
>            Priority: Minor
>             Fix For: 0.7.7, 0.8.2
>
>         Attachments: 2800.txt
>
>
> OPP#describeOwnership relies on StorageService#getSplits and counts the received tokens as its basis of ownership.
> When the number of result keys is less than the number of splits, the full count is omitted (to save work?). However, we don't care if a split would end up fractional in this case, we just need the full count.
> The logic here is:
> {code}
> int splits = keycount * DatabaseDescriptor.getIndexInterval() / keysPerSplit;
> if (keycount >= splits) { ... add count to result set }
> {code}
> We were passing in 1 key per split (since we just care about the count), but splits=keycount*IndexInterval is guaranteed to be > keycount, so the result set is not completely formed.
> The better "unit keysPerSplit" to use is IndexInterval itself, which gives splits=keycount*II/II=keycount, so the logic runs correctly.

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