what is the main differences between Lookup, Join and Merge
stages?
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Answer Posted / aishwarya
Join Stage:
1.) It has n input links(one being primary and remaining
being secondary links), one output link and there is no
reject link
2.) It has 4 join operations: inner join, left outer join,
right outer join and full outer join
3.) join occupies less memory, hence performance is high in
join stage
4.) Here default partitioning technique would be Hash
partitioning technique
5.) Prerequisite condition for join is that before
performing join operation, the data should be sorted.
Look up Stage:
1.) It has n input links, one output link and 1reject link
2.) It can perform only 2 join operations: inner join and
left outer join
3.) Join occupies more memory, hence performance reduces
4.) Here default partitioning technique would be Entire
Merge Stage:
1.) Here we have n inputs master link and update links andn-
1 reject links
2.) in this also we can perform 2 join operations: inner
join, left outer join
3.) the hash partitioning technique is used by default
4.) Memory used is very less, hence performance is high
5.) sorted data in master and update links are mandatory
| Is This Answer Correct ? | 61 Yes | 13 No |
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