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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6477) Partitioned indexes
Date Tue, 01 Apr 2014 16:11:31 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13956701#comment-13956701
] 

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

New suggestion:

Since we're performing read-before-write anyway with this suggestion, why not simply perform
a _local only_ read-before-write on each of the nodes that owns the main record whilst writing
the update - instead of issuing a complex tombstone, we simply issue a delete for whichever
value is older on reconcile.  Since we always CAS local updates, we will never get missed
deletes, however we will issue redundant/duplicate deletes (RF many) - but they should be
coalesced in memtable almost always, so it's a network cost only. There are probably tricks
we can do to mitigate this cost, though, e.g. having each node (deterministically) pick two
of the possible owners of the 2i entry to send the deletes it encounters to, to minimise replication
of effort but also ensure message delivery to all nodes.

Result is we keep compaction logic exactly the same, and we retain approximately the same
consistency guarantees we currently have.

> Partitioned 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
>             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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