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  1. Core Server
  2. SERVER-40043

$set takes quadratic time while holding locks

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    • Type: Icon: Bug Bug
    • Resolution: Duplicate
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: Querying
    • None
    • Query
    • ALL

      Confirmed in 3.6.8 and 4.0.6:

      from collections import OrderedDict
from pymongo import MongoClient

client = MongoClient()
d = client['test']
c = d['foo']

setDict = {}
numElements = 50000
for x in range(numElements):
    setDict['a'+str(x)] = 1

c.update_one({'_id':1},{'$set': setDict})
      Num Elements Duration
      50000 16s
      100000 70s
      150000 143s
      200000 257s

      Since this operation does not yield, it can block operations that require stronger locks stalling all operations.

      Typical stack in 4.0.6

      Thread 2 (Thread 0x7fda2f02f700 (LWP 1481)):
#0  0x00007fda3deb726b in mongo::mutablebson::Element::findFirstChildNamed(mongo::StringData) const ()
#1  0x00007fda3db9178e in mongo::(anonymous namespace)::getChild(mongo::mutablebson::Element, mongo::StringData) ()
#2  0x00007fda3db91ea0 in mongo::(anonymous namespace)::applyChild(mongo::UpdateNode const&, mongo::StringData, mongo::UpdateNode::ApplyParams*, mon
#3  0x00007fda3db941fa in mongo::UpdateObjectNode::apply(mongo::UpdateNode::ApplyParams) const ()
#4  0x00007fda3db76525 in mongo::UpdateDriver::update(mongo::StringData, mongo::mutablebson::Document*, bool, mongo::FieldRefSet const&, mongo::BSON
#5  0x00007fda3ce723cf in mongo::UpdateStage::transformAndUpdate(mongo::Snapshotted<mongo::BSONObj> const&, mongo::RecordId&) ()
#6  0x00007fda3ce73f6d in mongo::UpdateStage::doWork(unsigned long*) ()
#7  0x00007fda3ce4e96b in mongo::PlanStage::work(unsigned long*) ()
#8  0x00007fda3ce9f42d in mongo::PlanExecutor::getNextImpl(mongo::Snapshotted<mongo::BSONObj>*, mongo::RecordId*) ()
#9  0x00007fda3ce9fdbb in mongo::PlanExecutor::getNext(mongo::BSONObj*, mongo::RecordId*) ()
#10 0x00007fda3ce9feed in mongo::PlanExecutor::executePlan() ()
#11 0x00007fda3cc586c5 in mongo::performUpdates(mongo::OperationContext*, mongo::write_ops::Update const&) ()
#12 0x00007fda3cc5075d in mongo::(anonymous namespace)::CmdUpdate::Invocation::runImpl(mongo::OperationContext*, mongo::BSONObjBuilder&) const ()
#13 0x00007fda3cc4e8b2 in mongo::(anonymous namespace)::WriteCommand::InvocationBase::run(mongo::OperationContext*, mongo::CommandReplyBuilder*) ()
#14 0x00007fda3c63a6bc in mongo::(anonymous namespace)::execCommandDatabase(mongo::OperationContext*, mongo::Command*, mongo::OpMsgRequest const&, m
#15 0x00007fda3c63bda9 in mongo::(anonymous namespace)::receivedCommands(mongo::OperationContext*, mongo::Message const&, mongo::ServiceEntryPointCo
#16 0x00007fda3c63ccf1 in mongo::ServiceEntryPointCommon::handleRequest(mongo::OperationContext*, mongo::Message const&, mongo::ServiceEntryPointCom
#17 0x00007fda3c6284ba in mongo::ServiceEntryPointMongod::handleRequest(mongo::OperationContext*, mongo::Message const&) ()
#18 0x00007fda3c634fea in mongo::ServiceStateMachine::_processMessage(mongo::ServiceStateMachine::ThreadGuard) ()
#19 0x00007fda3c62fc67 in mongo::ServiceStateMachine::_runNextInGuard(mongo::ServiceStateMachine::ThreadGuard) ()
#20 0x00007fda3c6334b1 in std::_Function_handler<void (), mongo::ServiceStateMachine::_scheduleNextWithGuard(mongo::ServiceStateMachine::ThreadGuard
#21 0x00007fda3d7c0d72 in mongo::transport::ServiceExecutorSynchronous::schedule(std::function<void ()>, mongo::transport::ServiceExecutor::Schedule
#22 0x00007fda3c62de50 in mongo::ServiceStateMachine::_scheduleNextWithGuard(mongo::ServiceStateMachine::ThreadGuard, mongo::transport::ServiceExecu
#23 0x00007fda3c631035 in mongo::ServiceStateMachine::_sourceCallback(mongo::Status) ()
#24 0x00007fda3c62f3a7 in mongo::ServiceStateMachine::_sourceMessage(mongo::ServiceStateMachine::ThreadGuard) ()
#25 0x00007fda3c62fced in mongo::ServiceStateMachine::_runNextInGuard(mongo::ServiceStateMachine::ThreadGuard) ()
#26 0x00007fda3c6334b1 in std::_Function_handler<void (), mongo::ServiceStateMachine::_scheduleNextWithGuard(mongo::ServiceStateMachine::ThreadGuard
#27 0x00007fda3d7c12d5 in std::_Function_handler<void (), mongo::transport::ServiceExecutorSynchronous::schedule(std::function<void ()>, mongo::tran
#28 0x00007fda3de885f4 in mongo::(anonymous namespace)::runFunc(void*) ()
#29 0x00007fda3ac18184 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#30 0x00007fda3a94503d in clone () from /lib/x86_64-linux-gnu/libc.so.6

            Assignee:
            backlog-server-query Backlog - Query Team (Inactive)
            Reporter:
            kelsey.schubert@mongodb.com Kelsey Schubert
            Votes:
            1 Vote for this issue
            Watchers:
            19 Start watching this issue

              Created:
              Updated:
              Resolved: