<< std::make_pair( "extract_failed", nExtractFailed )
<< std::make_pair( "iterator_pass_count", nIteratorPassCount )
<< std::make_pair( "iterator_visit_count", nIteratorVisitCount )
<< std::make_pair( "extract_failed", nExtractFailed )
<< std::make_pair( "iterator_pass_count", nIteratorPassCount )
<< std::make_pair( "iterator_visit_count", nIteratorVisitCount )