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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6857) SELECT DISTINCT with a LIMIT is broken by paging
Date Thu, 20 Mar 2014 21:23:45 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13942298#comment-13942298
] 

Tyler Hobbs commented on CASSANDRA-6857:
----------------------------------------

The patches do seem to work (it was a little confusing that the 2.1 patch assumed the 2.0
patch was applied).

I have a question, though.  You said the QueryPagers change was an optimization, but it appears
to affect the correctness.  Without the QueryPagers change, the old behavior is still observed.
 I'm not 100% clear on why that is.  Can you explain?

> 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|https://datastax-oss.atlassian.net/browse/JAVA-288] and there is
a reproduction script there).



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