if RCP is used for Aggregator stage only those column will go to output , which are there in the mapping tab of aggregator on the left side(left side on the mapping tab).I have tried it once with sequential file as input to aggregator and sequential file as output to aggregator.
Think about it in SQL terms. What are the rules in SQL? Every column named in the SELECT clause, if there is a GROUP BY clause, must either be mentioned in the GROUP BY clause or have a set function applied to it.
A column propagated via RCP would meet neither of these conditions.
Therefore it would be illegal if it were possible.
Therefore it is not possible.
QED
IBM Software Services Group
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Do an exact search on "aggregator". This has been answered before. You would have to use Sort, Copy and Join stages along with Aggregator stage to get all the columns and the calculated field.