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Sylvain Lebresne commented on CASSANDRA-4476:
---------------------------------------------
Good question. This ticket was only ever meant to deal with {{LT}}, {{LTE}},
{{GTE}} and {{GT}} so let's leave it to that for this ticket (I've made the
title more precise). Regarding {{IN}}, it could be supported, but for the sake
of doing one thing at a time, it's probably better to leave it a as follow up
of this ticket. For {{NEQ}}, I see no way to do it in even a vaguely efficient
way (at least with the current indexing scheme) so I don't think there is any
plan to ever support it (but even if someone has a brilliant idea how to do it,
it's definitively a separate issue).
> 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
> Priority: Minor
> Labels: cql
> Fix For: 2.1.2
>
>
> 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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