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The "SecondaryIndexes" page has been changed by JimAncona: http://wiki.apache.org/cassandra/SecondaryIndexes?action=diff&rev1=2&rev2=3 Comment: Add question about Consistency Level and cluster availability * Q: Why is it necessary to always have at least one EQ comparison on secondary indices? A: Inequalities on secondary indices are always done in memory, so without at least one EQ on another secondary index you will be loading every row in the database, which with a massive database isn't a good idea. So by requiring at least one EQ on an index, you hopefully limit the set of rows that need to be read into memory to a manageable size. Although obviously you can still get into trouble with that as well. + * Q: How does choice of Consistency Level affect cluster availability when using secondary indexes? + A: Because secondary indexes are distributed, you must have CL level nodes available for all token ranges in the cluster in order to complete a query. For example, with RF = 3, when two out of three consecutive nodes in the ring are unavailable, all secondary index queries at CL = QUORUM will fail, however secondary index queries at CL = ONE will succeed. This is true regardless of cluster size. +
