What are the prerequisites for join stage

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What are the prerequisites for join stage..

Answer / niti

data should be hash partitioned & sorted.. :)

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What are the prerequisites for join stage..

Answer / shar

1.Inputs as left right and intermediate links(files).
2.can do left outer,right outer,inner join and full outer join
3.N inputs for left,right and inner but 2 inputs for full outer.
4.Inputs should be sorted and partitioned for better
performance.
5.Removing duplicates is optional as join operation is
highly optimized which sequential and less i/o and less page
faults.
6.Memory requirements are comparatively less than Lookup stage.
7.In join key columns names should be same in primary and
secondary datasets.

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