[jira] [Commented] (CASSANDRA-4476) Support 2ndary index queries with only non-EQ clauses

["Vicky Kak (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-4476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13994875#comment-13994875 ] 

Vicky Kak commented on CASSANDRA-4476:
--------------------------------------

{quote}
A priori, this ticket is not really all that hard. All we need to do is that when we query the index, instead of querying one index row, we support querying a range of them. After that, the rest of the index code should remain unchanged.
{quote}

Do we query the index via KeySearcher::search(..) method?


> Support 2ndary index queries with only non-EQ clauses
> -----------------------------------------------------
>
>                 Key: CASSANDRA-4476
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4476
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: API, Core
>            Reporter: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 2.1 rc1
>
>
> 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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