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From "Jeremy Hanna (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7520) Permit sorting sstables by raw partition key, as opposed to token
Date Wed, 27 Jan 2016 23:29:40 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15120402#comment-15120402
] 

Jeremy Hanna commented on CASSANDRA-7520:
-----------------------------------------

I think this is what [~iamaleksey] was getting at but range scans such as for spark queries
would no longer be contiguous.  Other than that, it sounds like there are instances where
it could be beneficial.

> Permit sorting sstables by raw partition key, as opposed to token
> -----------------------------------------------------------------
>
>                 Key: CASSANDRA-7520
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7520
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Benedict
>
> At the moment we have some counter-intuitive behaviour, which is that with a hashed partitioner
(recommended) the more compacted the data is, the more randomly distributed it is amongst
the file. This means that data access locality is made pretty much as bad as possible, and
we rely on the OS to do its best to fix that for us with its page cache.
> [~jasobrown] mentioned this at the NGCC, but thinking on it some more it seems that many
use cases may benefit from dropping the token at the storage level and sorting based on the
raw key data. For workloads where nearness of key => likelihood of being coreferenced,
this could improve data locality and cache hit rate dramatically. Timeseries workloads spring
to mind, but I doubt this is constrained to them. Most likely any non-random access pattern
could benefit. A random access pattern would most likely suffer from this scheme, as we can
index more efficiently into the hashed data. However there's no reason we could not support
both schemes. 



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