Sylvain Lebresne created CASSANDRA-4476:
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Summary: 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
Reporter: Sylvain Lebresne
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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