Rohini Palaniswamy created PIG-4885:
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Summary: 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
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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