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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6477) Materialized Views (was: Global Indexes)
Date Fri, 24 Jul 2015 15:35:09 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14640602#comment-14640602
] 

Benedict commented on CASSANDRA-6477:
-------------------------------------

OK, so we have deadlock in that case. The apply of the batchlog happens on a separate writeOrder
group. The earlier group could be marked as "blocking" in which case it is permitted to take
any necessary action to terminate, but a later (or even simply different keyspace) group is
_not_ marked blocking and we depend on it, then the system will lock up. In fact, we have
this twice: once for batchlog, once for the MV mutation (if local).

We could also do with some comments around things like: 

{code}

        if (stage != Stage.MATERIALIZED_VIEW_MUTATION)
        {
            for (WriteResponseHandlerWrapper wrapper : wrappers)
                wrapper.handler.get();
        }
{code}

Without any context, it's kind of hard to spot let alone understand the important semantic
difference and why it is there.

In general, I'd prefer more comments around this feature.

> 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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