maverickwild

 Profile Answers by maverickwild 

• Apr 9th, 2006

 

When you use aggregator transformation to aggregate it creates index and data caches to store the data 1.Of group By columns 2. Of aggreagte columns

the incremental aggreagtion is used when we have historical data in place which will be used in aggregation incremental aggregation uses the cache which contains the historical data and for each group by column value already present in cache it add the data value to its corresponding data cache value and outputs the row , in case of a incoming value having no match in index cache the new values for group by and output ports are inserted into the cache .

Shanmugam

• Jul 5th, 2006

 

Incremental aggregation is specially used for tune the performance of the aggregator. It captures the change each time (incrementally) you run the transformation and then performs the aggregation function to the changed rows and not to the entire rows. This improves the performance because you are not reading the entire source, each time you run the session.