[optim] cache rset column structures When iterating over large resultsets (lot of colcumns, lot of lines) to build entities, caching column structure (which attribute or relation is stored in each column) can improve performance noticeably.

include *.py
include */*.py
recursive-include data *.gif *.png *.ico *.css *.js
recursive-include i18n *.po
recursive-include wdoc *