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From "Philip Thompson (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-10010) Paging on DISTINCT queries repeats result when first row in partition changes
Date Fri, 05 Feb 2016 15:35:40 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-10010?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Philip Thompson updated CASSANDRA-10010:
----------------------------------------
    Fix Version/s:     (was: 2.2.x)
                   2.2.6

> Paging on DISTINCT queries repeats result when first row in partition changes
> -----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-10010
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10010
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Tyler Hobbs
>            Assignee: Benjamin Lerer
>            Priority: Minor
>             Fix For: 2.2.6
>
>         Attachments: 10010-2.2.txt
>
>
> When paging, we always check new pages to see if they start with the same row that the
previous page ended with, and if so, we trim that row to avoid duplicates.  With {{DISTINCT}}
queries, we only fetch the first row in each partition.  If that row happens to change (it's
deleted, or another row is inserted at the front of the partition) in between fetching the
two pages, our check for a matching row will fail, resulting in a duplicate row being returned.
> It seems like the correct fix is to handle {{DISTINCT}} queries specially and only check
to see if the partition key matches the last returned one instead checking that the rows match.



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