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Posted to dev@pig.apache.org by "liyunzhang_intel (JIRA)" <ji...@apache.org> on 2016/02/15 08:47:18 UTC
[jira] [Updated] (PIG-4601) Implement Merge CoGroup for Spark
engine
[ https://issues.apache.org/jira/browse/PIG-4601?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
liyunzhang_intel updated PIG-4601:
----------------------------------
Status: Patch Available (was: Open)
> Implement Merge CoGroup for Spark engine
> ----------------------------------------
>
> Key: PIG-4601
> URL: https://issues.apache.org/jira/browse/PIG-4601
> Project: Pig
> Issue Type: Sub-task
> Components: spark
> Affects Versions: spark-branch
> Reporter: Mohit Sabharwal
> Assignee: liyunzhang_intel
> Fix For: spark-branch
>
> Attachments: PIG-4601_1.patch, PIG-4601_2.patch
>
>
> When doing a cogroup operation, we need do a map-reduce. The target of merge cogroup is implementing cogroup only by a single stage(map). But we need to guarantee the input data are sorted.
> There is performance improvement for cases when A(big dataset) merge cogroup B( small dataset) because we first generate an index file of A then loading A according to the index file and B into memory to do cogroup. The performance improves because there is no cost of reduce period comparing cogroup.
> How to use
> {code}
> C = cogroup A by c1, B by c1 using 'merge';
> {code}
> Here A and B is sorted.
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