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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-6857) SELECT DISTINCT with a LIMIT is broken by paging
Date Fri, 14 Mar 2014 16:02:43 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-6857?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sylvain Lebresne updated CASSANDRA-6857:
----------------------------------------

    Attachment: 6857-2.1.txt
                6857-2.0.txt

In theory, the problem is that PagedRangeCommand doesn't preserve the countCQ3Rows parameter
of the original RangeSliceCommand. However, on 2.0, we can't add it as this is a breaking
messaging protocol change. Fortunately, we can work around that easily enough, see the attached
patch. I still attach a patch for 2.1 that "does the right thing" because that's less of a
hack on the long run. Note that the QueryPagers change is a minor optimization that is not
entirely related to the fix of this issue, but that's easy enough.

> SELECT DISTINCT with a LIMIT is broken by paging
> ------------------------------------------------
>
>                 Key: CASSANDRA-6857
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6857
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>             Fix For: 2.0.7
>
>         Attachments: 6857-2.0.txt, 6857-2.1.txt
>
>
> The paging for RangeSliceCommand only support the case where we count CQL3 rows . However,
in the case of SELECT DISTINCT, we do actually want to use the "count partitions, not CQL3
row" path and that's currently broken when the paging commands are used (this was first reported
on the [Java driver JIRA|thttps://datastax-oss.atlassian.net/browse/JAVA-288] and there is
a reproduction script there).



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