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https://issues.apache.org/jira/browse/CASSANDRA-4983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13709111#comment-13709111
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Jonathan Ellis commented on CASSANDRA-4983:
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I'm not really a fan of making CFRR (and CqlPRR?) more complex to make a corner
case slightly better. Remember, we'll have exactly one wrapping range per Task
out of the 100s of splits.
On the bright side, the "real" CqlInputFormat (using server-side paging) will
make this a non-issue in 2.0.
> 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
> Fix For: 1.2.7
>
> Attachments:
> 0001-CASSANDRA-4983-CFRR-able-to-iterate-over-more-than-o.patch
>
>
> 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.
> * Progress reporting for the divided split parts is inaccurate - even if the
> splits are similar in size, the progress bar goes to about 50% and then
> immediately to 100%, because it is impossible to estimate their size properly
> (the size estimation is done before removing wrap-around).
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