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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6477) Global indexes
Date Mon, 16 Mar 2015 20:25:42 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14363846#comment-14363846
] 

Jonathan Ellis commented on CASSANDRA-6477:
-------------------------------------------

On the one hand, all queries that would be valid w/o GI should still be valid -- with similar
caveats to 2i, i.e., filtering on 2 GI columns won't actually be faster than 1 GI and 1 non-indexed-but-included
column, until we have actual multi-column indexes.

On the other hand, GI introduces a new way to introduce a query that is much slower than expected
-- if you filter on a column that is not included in the GI, then you need to fall back to
seq scan on the base table.

> Global indexes
> --------------
>
>                 Key: CASSANDRA-6477
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6477
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: API, Core
>            Reporter: Jonathan Ellis
>            Assignee: Carl Yeksigian
>              Labels: cql
>             Fix For: 3.0
>
>
> Local indexes are suitable for low-cardinality data, where spreading the index across
the cluster is a Good Thing.  However, for high-cardinality data, local indexes require querying
most nodes in the cluster even if only a handful of rows is returned.



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