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From "Roland Gude (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4332) IndexRangeSliceQuery results contain IndexColumn even though it is not included in SliceRange
Date Wed, 13 Jun 2012 07:53:42 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13294244#comment-13294244
] 

Roland Gude commented on CASSANDRA-4332:
----------------------------------------

i think i understand the issue now:

It is dependant on Consistency Level/Replication and our usage of index queries (which i guess
several other people are using similar)

What we do is a index query and paging over the results (i.e. request 100 rows, if we get
100 rows - fetch next 100 if we get less, stop)

Using consistency level one apparently there is a situation where the node which started the
query cannot satisfy the number of requested rows and simply returns those he has - which
is less then the expected number of rows. so paging thinks there is nothing more and just
stops.

Using consistency level ALL (or Quorum) the request seems to reach the node which has the
replica as well. That node now adds to the results the local indexed rows starting from the
given token. The results are merged and returned. now - if first node cannot satisfy the number
of requested rows - the result will contain items from a node with another token range and
paging can continue on that other node.

If this is the case, this comes with several caveats.

In order to get consistent results from a paging index query, it is required to either - page
over all tokensranges from the cluster manually
or use consistency level ALL and make sure that replication layout gives you adjacent token
ranges (i.e. SimpleStrategy). Any other strategy might mess up results, I guess.

does this sound at least half way reasonable?

                
> IndexRangeSliceQuery results contain IndexColumn even though it is not included in SliceRange
> ---------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-4332
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4332
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 1.1.1
>            Reporter: Roland Gude
>         Attachments: system.log, system.log
>
>
> This is the magical reappearance of CASSANDRA-2964 

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