Hive, mail # user - Will this UDF always execute on a single reducer ? - 2014-03-01, 03:57
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Will this UDF always execute on a single reducer ?
Hi,

I have written a custom UDF that I want to be executed on a single reducer
when I am using it in a query. Following is the the query  and  I want to
confirm whether this would always always execute the UDF on a single
reducer (assuming the ORDER BY would send all the rows  to a single
reducer):
*SELECT UDF(<col>) AS alias  from *

*( SELECT <col> *

*  FROM  <table> TABLESAMPLE (x PERCENT) *

*  ORDER BY <col> )*

*ORDER BY alias;*
Is it a possibility that the UDF is executed on a mapper?

Thanks
Vaibhav Jain

 
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