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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-7520) Permit sorting sstables by raw partition key, as opposed to token
Date Tue, 08 Jul 2014 18:49:06 GMT
Benedict created CASSANDRA-7520:
-----------------------------------

             Summary: 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
          Components: Core
            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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