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Date: Fri, 12 Dec 2014 13:55:16 +0000 (UTC)
From: "Sylvain Lebresne (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-4476) Support 2ndary index queries
 with only inequality clauses (LT, LTE, GT, GTE)
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    [ https://issues.apache.org/jira/browse/CASSANDRA-4476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14244155#comment-14244155 ] 

Sylvain Lebresne commented on CASSANDRA-4476:
---------------------------------------------

It should be possible to page despite the fact results are not in token order (after all, the order is deterministic) but we'd need to look at it more closely to assess if the complexity of that would be worth it or not, so I'll at least push this to 3.1 for now.  

> Support 2ndary index queries with only inequality clauses (LT, LTE, GT, GTE)
> ----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-4476
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4476
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: API, Core
>            Reporter: Sylvain Lebresne
>            Assignee: Oded Peer
>            Priority: Minor
>              Labels: cql
>             Fix For: 3.1
>
>         Attachments: 4476-2.patch, 4476-3.patch, 4476-5.patch, cassandra-trunk-4476.patch
>
>
> Currently, a query that uses 2ndary indexes must have at least one EQ clause (on an indexed column). Given that indexed CFs are local (and use LocalPartitioner that order the row by the type of the indexed column), we should extend 2ndary indexes to allow querying indexed columns even when no EQ clause is provided.
> As far as I can tell, the main problem to solve for this is to update KeysSearcher.highestSelectivityPredicate(). I.e. how do we estimate the selectivity of non-EQ clauses? I note however that if we can do that estimate reasonably accurately, this might provide better performance even for index queries that both EQ and non-EQ clauses, because some non-EQ clauses may have a much better selectivity than EQ ones (say you index both the user country and birth date, for SELECT * FROM users WHERE country = 'US' AND birthdate > 'Jan 2009' AND birtdate < 'July 2009', you'd better use the birthdate index first).


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