> Then if I do copy command to move it into truncate_document > then even though > I can reduce it down to say 100 words, it is lacking words > like "and" "it" > and "this" because it has been copied from the > keyword_document.
That's not true. copy operation is performed before analysis (stopword removal, lowercasing etc). It will copy raw text of keyword_document field. It has noting to do with analysis of source field.
