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From Piotr Kołaczkowski (JIRA) <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-4983) Improve range wrap-around in CFIF: CFIF shouldn't produce input splits of very tiny size
Date Thu, 22 Nov 2012 09:08:58 GMT
Piotr Kołaczkowski created CASSANDRA-4983:
---------------------------------------------

             Summary: Improve range wrap-around in CFIF: CFIF shouldn't produce input splits
of very tiny size
                 Key: CASSANDRA-4983
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4983
             Project: Cassandra
          Issue Type: Improvement
    Affects Versions: 1.1.6
            Reporter: Piotr Kołaczkowski
            Assignee: Piotr Kołaczkowski
            Priority: Minor


Currently CFIF splits the wrap-around split into two non-wrap-around splits. While it simplifies
CFRR implementation, this approach has several minor downsides:

 * One of the splits can be extremely small. One of our (picky) customers suspected there
must be a bug, because one of his map tasks executed in 1  second, while all the rest executed
in minutes. Also having a very small task is wasting resources - more resources go to launching
the task than doing any real work.

 * The number of map tasks is always one more than the number of (expected rows / cassandra.input.split.size).
The number of map tasks is always >= 2. This is confusing customers. 

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