if finding the first object is slow, update doesn't yield.

Constructors should be instantanous

only next() should iterate,

(gdb)
#0 std::vector<boost::shared_ptr<mongo::QueryOp>, std::allocator<boost::shared_ptr<mongo::QueryOp> > >::size (this=0x0) at stl_vector.h:399
#1 0x000000010009f9f2 in mongo::QueryPlanSet::Runner::run (this=0x101708e30) at db/queryoptimizer.cpp:551
#2 0x00000001000a1e65 in mongo::QueryPlanSet::runOp (this=0x101011f40, op=@0x101011710) at db/queryoptimizer.cpp:460
#3 0x00000001000a2175 in mongo::MultiPlanScanner::runOpOnce (this=0x101010b70, op=@0x101011710) at db/queryoptimizer.cpp:642
#4 0x000000010006fdd6 in mongo::MultiPlanScanner::runOpOnce<mongo::MultiCursor::CursorOp> (this=0x101010b70, op=@0x101011710) at queryoptimizer.h:266
#5 0x000000010006ccc5 in mongo::MultiCursor::nextClause (this=0x1010117b0) at queryoptimizer.h:366
#6 0x000000010006db75 in mongo::MultiCursor::MultiCursor (this=0x1010117b0, ns=0x101814a14 "mongo-test.perf", pattern=@0x1017097f0, order=@0x101709580, op=@0x101709620) at queryoptimizer.h:308
#7 0x0000000100148e8a in mongo::_updateObjects (god=false, ns=0x101814a14 "mongo-test.perf", updateobj=@0x101709930, patternOrig=@0x1017097f0, upsert=false, multi=false, logop=true, debug=@0x108000a70) at db/update.cpp:896
#8 0x000000010014a61b in mongo::updateObjects (ns=0x101814a14 "mongo-test.perf", updateobj=@0x101709930, patternOrig=@0x101709910, upsert=false, multi=false, logop=true, debug=@0x108000a70) at db/update.cpp:1109
#9 0x00000001001b2f01 in mongo::receivedUpdate (m=@0x101709df0, op=@0x108000820) at db/instance.cpp:455
#10 0x00000001001b4bd2 in mongo::assembleResponse (m=@0x101709df0, dbresponse=@0x101709d40, client=@0x108000318) at db/instance.cpp:323
#11 0x000000010023ded3 in mongo::connThread () at db/db.cpp:247
#12 0x00000001000de25d in boost::detail::thread_data<void ()>::run (this=0x108000420) at thread.hpp:56
#13 0x0000000100def404 in thread_proxy ()
#14 0x00007fff8280d456 in _pthread_start ()