Hash file stage-Active or passive stage?

sumesh.abraham · Post by **sumesh.abraham** » Thu Sep 20, 2007 1:43 am

Hi All,

Whether hash file stage is an active stage or passive stage?. My understanding says active stages are stages which perform processing tasks whereas passive stages do not do processing tasks and just offer services to the active stages. Please let me know.

Thanks,
Sumesh

ArndW · Post by **ArndW** » Thu Sep 20, 2007 1:48 am

Your understanding is correct, and by that token a Hashed file stage (notice the difference in spelling, otherwise Ray will pounce on you) is a passive stage.

sumesh.abraham · Post by **sumesh.abraham** » Thu Sep 20, 2007 2:32 am

Thanks a lot Arndw.

ray.wurlod · Post by **ray.wurlod** » Thu Sep 20, 2007 4:20 pm

Active stages have the potential to change the data flowing through them. While simplistic, that's not a bad way to differentiate. You could always inspect the stage type properties in the Stage Types branch of the Repository - the General tab indicates whether the stage type is active or passive or neither (I leave the last as an exercise for the reader.)

praveensuss · Post by **praveensuss** » Fri Sep 21, 2007 12:21 pm

Hashed file is a Passive stage..

Actives stages, such as the Transformer and Aggregator perform processing tasks, while passive stages, such as Sequential file stage, hashed file stage and ODBC stage, are reading or writing data sources and provide services to the active stages.

Hope this clarifies your query !!!

Cheers!!
Praveen

Amit_111 · Post by **Amit_111** » Sat Sep 22, 2007 12:54 am

How come a Hashed file is a Passive Stage??............If we go by the definition of Active stages and see that even hashed files perform Hashing Algorithms( which is a kind of processing on Data), Also adding to it the hashed files do the work of removing duplicates from the source based on the keys defined.....looking at these things it should be called as an active stage(even if it might not be)........

ArndW · Post by **ArndW** » Sat Sep 22, 2007 1:06 am

Umm, by that token a sequential file stage is also active, since it opens and writes to files and allows pre- and postprocessing to be done as well. The definitive definitions can be found in the metadata describing these stages, the rest is just theorizing.

I like to look at passive stages as being sources or targets of data; anything else is an active stage.

ray.wurlod · Post by **ray.wurlod** » Sat Sep 22, 2007 6:25 am

Applying a hashing algorithm does not change the data; it only locates a key in one of a finite number of groups (pages). Most (if not all) passive stages are capable of destructive overwrite; this is not a change to the record being processed.