Hello *, reading this page states only that iterator validity is preserved for hashed indices. I have a multi-index container with ordered_non_unique entries. Is it safe to find a matching range and modify the keys there? Here an example: entry_data& entries = indexed; //get the view to the MI-Container for(iterator_range<entry_data::iterator> r = entries.equal_range(boost::make_tuple(false)) ; !r.empty() ; r.advance_begin(1) ) { index_data d = r.front(); d.masked = true; entries.replace(r.begin(), d); } Here updated d.masked field is a first member of the composite key. What happens if I do the update as shown upon? Would it be more efficient to iterate backwards and do the update, since than all the elements will not be rearranged? Is there also any way to use modify_key with composite index or are composite index key extractors always read-only? With Kind Regards, Ovanes