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https://issues.apache.org/jira/browse/CASSANDRA-6477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14626399#comment-14626399
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T Jake Luciani commented on CASSANDRA-6477:
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bq. Creating a MV where the partition key is for instance the gender of your
users is equally going to create massive hotspots, but it's not like we can
forbid people to do it.
This is an obvious anti-pattern for a materialized view. NULL, however, is not
something people think about since it's the default value implicitly for
Cassandra. Especially when considering consistency issues in a dynamo system.
If you are writing to a table with RF=3 and only one replica has a value but
the other two do not then we will make one MV replica have a defined partition
key and the other two replicas will have a NULL. Currently we don't allow this
so the NULLs are left out.
> Materialized Views (was: 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 beta 1
>
> Attachments: test-view-data.sh, users.yaml
>
>
> 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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