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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6477) Materialized Views (was: Global Indexes)
Date Wed, 15 Jul 2015 07:43:08 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14627670#comment-14627670
] 

Sylvain Lebresne commented on CASSANDRA-6477:
---------------------------------------------

bq. When we actually add support for null partition keys we can lift this requirement.

I do want to note that there *is* a technical problem with allowing null in the MV primary
keys (partition key or clustering columns alike), and that is TTLs. More precisely, if a column
{{c}} in the MV PK has a TTL, we would need to update the MV once {{c}} expires, replacing
the entry by one where {{c}} is now {{null}}. And a priori, I don't see an even remotely efficient
way to deal with that (keeping in mind that we collect expired column lazily, *not* when they
expire).

That is, I agree that requiring {{IS NOT NULL}} for all *primary* key columns is the safe
option for 3.0, but just wanted to note that the TTL problem above seems to me like a big
obstacle in removing that requirement.


> 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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