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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1337) parallelize fetching rows for low-cardinality indexes
Date Thu, 08 Nov 2012 16:04:16 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13493273#comment-13493273
] 

Sylvain Lebresne commented on CASSANDRA-1337:
---------------------------------------------

Sorry I haven't been able to got to that sooner. This will thus need rebasing. Also, I'm pretty
sure the is something specific to do to make that work for get_paged_slice. I wouldn't be
against just deactivating this parallelization for get_paged_slice to start with.
                
> parallelize fetching rows for low-cardinality indexes
> -----------------------------------------------------
>
>                 Key: CASSANDRA-1337
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1337
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: David Alves
>            Priority: Minor
>             Fix For: 1.2.0 rc1
>
>         Attachments: 1137-bugfix.patch, 1337.patch, 1337-v4.patch, ASF.LICENSE.NOT.GRANTED--0001-CASSANDRA-1337-scan-concurrently-depending-on-num-rows.txt,
CASSANDRA-1337.patch
>
>   Original Estimate: 8h
>  Remaining Estimate: 8h
>
> currently, we read the indexed rows from the first node (in partitioner order); if that
does not have enough matching rows, we read the rows from the next, and so forth.
> we should use the statistics fom CASSANDRA-1155 to query multiple nodes in parallel,
such that we have a high chance of getting enough rows w/o having to do another round of queries
(but, if our estimate is incorrect, we do need to loop and do more rounds until we have enough
data or we have fetched from each node).

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