question about join/lookup

wuruima · Post by **wuruima** » Thu Nov 20, 2014 2:16 am

Hi dear friend,

would you please help to clarify the usage of join stage and lookup stage ?
I have below questions.
1, in join stage, is it necessary to sort both input links ? what will happen if we don't sort but just patition the input data by the keys?

2, sometimes the join stage and lookup stage can do the same time, in what condition should i use join stage, and when should i use lookup?

Thanks!

ray.wurlod · Post by **ray.wurlod** » Thu Nov 20, 2014 2:53 am

Join stage needs sorted inputs for efficiency. With sorted inputs it only needs to deal with a single key value at a time. Depending on your settings, if you don't sort your data DataStage will insert a tsort operator so that they are sorted (you can see this in the score).

Lookup can't do right outer join or full outer join. Lookup can't work with a reference data set that won't fit in memory.

wuruima · Post by **wuruima** » Thu Nov 20, 2014 3:33 am

ray.wurlod wrote:Join stage needs sorted inputs for efficiency. With sorted inputs it only needs to deal with a single key value at a time. Depending on your settings, if you don't sort your data DataStage will inse ...

Thanks for your reply but "inse" means ???

chulett · Post by **chulett** » Thu Nov 20, 2014 8:24 am

It means you cannot see the complete message because you are not a Premium user.