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https://issues.apache.org/jira/browse/PIG-4885?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rohini Palaniswamy updated PIG-4885:
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Resolution: Fixed
Hadoop Flags: Reviewed
Status: Resolved (was: Patch Available)
Committed to branch 0.16 and trunk. Thanks for the review Daniel.
> Turn off union optimizer if there is PARALLEL clause in union in Tez
> --------------------------------------------------------------------
>
> Key: PIG-4885
> URL: https://issues.apache.org/jira/browse/PIG-4885
> Project: Pig
> Issue Type: Improvement
> Reporter: Rohini Palaniswamy
> Assignee: Rohini Palaniswamy
> Fix For: 0.16.0
>
> Attachments: PIG-4885-1.patch
>
>
> In mapreduce, if PARALLEL clause was specified on UNION it was ignored as it
> was a map operation and split size was used. In Tez, when union optimizer is
> turned off it is a reduce side operation and we should let user control
> parallelism instead of relying on just auto-parallelism. This is specifically
> useful when user needs to control the number of output files.
> data = UNION A, B, C, D, E, F, G, H, I, J;
> store data;
> In the above case instead of manually controlling parallelism of A to J
> aliases to achieve desired parallelism the UNION clause can specify the
> desired parallelism using PARALLEL. i.e
> data = UNION A, B, C, D, E, F, G, H, I, J PARALLEL 50;
> This only works today if we set pig.tez.opt.union=false. We should
> automatically and selectively turn off union optimization for those unions
> that have PARALLEL clause.
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