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https://issues.apache.org/jira/browse/CRUNCH-51?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13456920#comment-13456920
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Gabriel Reid commented on CRUNCH-51:
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I was just doing some general testing with this, and ran into a couple of
issues:
- it seems that this patch doesn't work with descending (i.e. reverse-order)
sorting. When I tried reverse-order sorting strings, I got an IOException with
"Split points are out of order"
- sorting reflection-based Avro or generic records in Avro doesn't seem to work
-- in both cases I got a message of "Number of keys to write in partion file:0"
and then a materialize crashes due to the file to be materialized not existing
Apart from these issues, I think it's looking pretty good. The Avro reflection
sorting issue seems pretty minor to me (i.e. not a very common use case), but
this is something that does work right now with the single-reducer solution.
> PCollection#sort relies on using a single reducer for total order sorting
> -------------------------------------------------------------------------
>
> Key: CRUNCH-51
> URL: https://issues.apache.org/jira/browse/CRUNCH-51
> Project: Crunch
> Issue Type: Improvement
> Affects Versions: 0.3.0
> Reporter: Gabriel Reid
> Attachments: 0001-CRUNCH-51-Total-Order-Sort.patch, CRUNCH-51.patch
>
>
> The total-order sorting provided by the Sort class (and therefore
> PCollection#sort) relies on using a single reducer in order to provide
> total-order sorting. This is very inefficient for large datasets, and should
> be replaced with a total order partitioner instead.
> For more information, see CRUNCH-23 (and possibly also MAPREDUCE-4574).
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