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https://issues.apache.org/jira/browse/CASSANDRA-6477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14631354#comment-14631354
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T Jake Luciani commented on CASSANDRA-6477:
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bq. I've actually never understood why we do a batchlog update on the base
table replicas (and so I think we should remove it, even though that's likely
not the most costly one). Why do we need it? If my reasoning above is correct,
the coordinator batchlog is enough to guarantee durability and eventual
consistency because we will replay the whole mutation until a QUORUM of replica
acknowledges success.
Yes, if we error out if the base is unable to replicate to the view then the
second BL is redundant. However there are a few reasons why we did what we did.
1. Your availability is cut in half when you use a MV with these guarantees. I
have a 5 node cluster RF=3 and I want to write at CL.ONE. If I have an MV I
can no longer handle two down nodes. Since the paired replica for the one base
node might be down.
2. The cost of replaying the coordinator BL is much higher than replaying the
base to replica BL since the latter is 1:1.
I do agree there is a disconnect in terms of consistency level when using the
MV but the batchlog feature was written to handle this. We could support both
approaches in terms of a new flag? Or are we willing to take a hit on
availability?
> 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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