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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-1337) parallelize fetching rows for low-cardinality indexes
Date Thu, 26 Jul 2012 09:46:35 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-1337?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sylvain Lebresne updated CASSANDRA-1337:
----------------------------------------

    Priority: Major  (was: Minor)

(changing the priority to major because basically I think that currently it does more harm
than good, and we should either fix it before release or revert it)
                
> 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
>             Fix For: 1.2
>
>         Attachments: 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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