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https://issues.apache.org/jira/browse/PIG-545?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pradeep Kamath updated PIG-545:
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Attachment: PIG-545-v4.patch
Attached patch which addresses observation (1) in the previous comment.
Regarding (2), the differences from the current SortPartitioner are:
- In the configure of the WeightedRangePartitioner the entire sample file is
loaded and a hash is built for those sample elements which repeat across
partition boundaries - this is more expensive than previously but one time set
up
- IN the getPartition() call, if the input element is present in the hash, then
probabilistically a partition is assigned based on the information in the hash
else (as previously), a binary search of the quantiles array is done to figure
out the partition - overall this should be nearly the same as previously
performance wise.
Regarding (3), getPartition() is a hadoop interface method and hence we cannot
throw any other exception besides RuntimeException
> PERFORMANCE: Sampler for order bys does not produce a good distribution
> -----------------------------------------------------------------------
>
> Key: PIG-545
> URL: https://issues.apache.org/jira/browse/PIG-545
> Project: Pig
> Issue Type: Bug
> Components: impl
> Affects Versions: types_branch
> Reporter: Alan Gates
> Assignee: Pradeep Kamath
> Fix For: types_branch
>
> Attachments: PIG-545-v3.patch, PIG-545-v4.patch, WRP.patch, WRP1.patch
>
>
> In running tests on actual data, I've noticed that the final reduce of an
> order by has skewed partitions. Some reduces finish in a few seconds while
> some run for 20 minutes. Getting a better distribution should lead to much
> better performance for order by.
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