SERVER-57391 Return error response to OP_QUERY and OP_GET_MORE messages

1 files changed, 0 insertions, 673 deletions

diff --git a/src/mongo/db/query/find.cpp b/src/mongo/db/query/find.cpp
index c4dac17cfec..0f791f2d11e 100644
--- a/src/mongo/db/query/find.cpp
+++ b/src/mongo/db/query/find.cpp
@@ -78,9 +78,6 @@ using std::unique_ptr;
 // Failpoint for checking whether we've received a getmore.
 MONGO_FAIL_POINT_DEFINE(failReceivedGetmore);
 
-// Failpoint to keep a cursor pinned.
-MONGO_FAIL_POINT_DEFINE(legacyGetMoreWaitWithCursor)
-
 bool shouldSaveCursor(OperationContext* opCtx,
                       const CollectionPtr& collection,
                       PlanExecutor::ExecState finalState,
@@ -148,674 +145,4 @@ void endQueryOp(OperationContext* opCtx,
     }
 }
 
-namespace {
-
-/**
- * Uses 'cursor' to fill out 'bb' with the batch of result documents to be returned by this getMore.
- *
- * Returns the number of documents in the batch in 'numResults', which must be initialized to
- * zero by the caller. Returns the final ExecState returned by the cursor in *state.
- *
- * Throws an exception if the PlanExecutor encounters a failure.
- */
-void generateBatch(int ntoreturn,
-                   ClientCursor* cursor,
-                   BufBuilder* bb,
-                   std::uint64_t* numResults,
-                   ResourceConsumption::DocumentUnitCounter* docUnitsReturned,
-                   PlanExecutor::ExecState* state) {
-    PlanExecutor* exec = cursor->getExecutor();
-
-    try {
-        BSONObj obj;
-        while (!FindCommon::enoughForGetMore(ntoreturn, *numResults) &&
-               PlanExecutor::ADVANCED == (*state = exec->getNext(&obj, nullptr))) {
-
-            // If we can't fit this result inside the current batch, then we stash it for later.
-            if (!FindCommon::haveSpaceForNext(obj, *numResults, bb->len())) {
-                exec->enqueue(obj);
-                break;
-            }
-
-            // Add result to output buffer.
-            bb->appendBuf((void*)obj.objdata(), obj.objsize());
-
-            // Count the result.
-            (*numResults)++;
-
-            docUnitsReturned->observeOne(obj.objsize());
-        }
-    } catch (DBException& exception) {
-        auto&& explainer = exec->getPlanExplainer();
-        auto&& [stats, _] = explainer.getWinningPlanStats(ExplainOptions::Verbosity::kExecStats);
-        LOGV2_ERROR(20918, "getMore executor error", "stats"_attr = redact(stats));
-        exception.addContext("Executor error during OP_GET_MORE");
-        throw;
-    }
-}
-
-Message makeCursorNotFoundResponse() {
-    const int initialBufSize = 512 + sizeof(QueryResult::Value);
-    BufBuilder bb(initialBufSize);
-    bb.skip(sizeof(QueryResult::Value));
-    QueryResult::View qr = bb.buf();
-    qr.msgdata().setLen(bb.len());
-    qr.msgdata().setOperation(opReply);
-    qr.setResultFlags(ResultFlag_CursorNotFound);
-    qr.setCursorId(0);
-    qr.setStartingFrom(0);
-    qr.setNReturned(0);
-    return Message(bb.release());
-}
-
-}  // namespace
-
-/**
- * Called by db/instance.cpp.  This is the getMore entry point.
- */
-Message getMore(OperationContext* opCtx,
-                const char* ns,
-                int ntoreturn,
-                long long cursorid,
-                bool* exhaust,
-                bool* isCursorAuthorized) {
-    invariant(ntoreturn >= 0);
-
-    LOGV2_DEBUG(20909, 5, "Running getMore", "cursorId"_attr = cursorid);
-
-    CurOp& curOp = *CurOp::get(opCtx);
-    curOp.ensureStarted();
-
-    // For testing, we may want to fail if we receive a getmore.
-    if (MONGO_unlikely(failReceivedGetmore.shouldFail())) {
-        MONGO_UNREACHABLE;
-    }
-
-    *exhaust = false;
-
-    const NamespaceString nss(ns);
-
-    ResourceConsumption::ScopedMetricsCollector scopedMetrics(opCtx, nss.db().toString());
-
-    // Cursors come in one of two flavors:
-    //
-    // - Cursors which read from a single collection, such as those generated via the find command.
-    //   For these cursors, we hold the appropriate collection lock for the duration of the getMore
-    //   using AutoGetCollectionForRead. These cursors have the 'kLockExternally' lock policy.
-    //
-    // - Cursors which may read from many collections, e.g. those generated via the aggregate
-    //   command, or which do not read from a collection at all, e.g. those generated by the
-    //   listIndexes command. We don't need to acquire locks to use these cursors, since they either
-    //   manage locking themselves or don't access data protected by collection locks. These cursors
-    //   have the 'kLocksInternally' lock policy.
-    //
-    // While we only need to acquire locks for 'kLockExternally' cursors, we need to create an
-    // AutoStatsTracker in either case. This is responsible for updating statistics in CurOp and
-    // Top. We avoid using AutoGetCollectionForReadCommand because we may need to drop and reacquire
-    // locks when the cursor is awaitData, but we don't want to update the stats twice.
-    UninterruptibleLockGuard noInterrupt(opCtx->lockState());
-    boost::optional<AutoGetCollectionForReadMaybeLockFree> readLock;
-    boost::optional<AutoStatsTracker> statsTracker;
-
-    // These are set in the QueryResult msg we return.
-    int resultFlags = ResultFlag_AwaitCapable;
-
-    auto cursorManager = CursorManager::get(opCtx);
-    auto statusWithCursorPin = cursorManager->pinCursor(opCtx, cursorid);
-    if (statusWithCursorPin == ErrorCodes::CursorNotFound) {
-        return makeCursorNotFoundResponse();
-    }
-    uassertStatusOK(statusWithCursorPin.getStatus());
-    auto cursorPin = std::move(statusWithCursorPin.getValue());
-
-    // Set kMajorityCommitted before we instantiate readLock. We should not override readSource
-    // after storage snapshot is setup.
-    const auto replicationMode = repl::ReplicationCoordinator::get(opCtx)->getReplicationMode();
-    if (replicationMode == repl::ReplicationCoordinator::modeReplSet &&
-        cursorPin->getReadConcernArgs().getLevel() ==
-            repl::ReadConcernLevel::kMajorityReadConcern) {
-        opCtx->recoveryUnit()->setTimestampReadSource(RecoveryUnit::ReadSource::kMajorityCommitted);
-        uassertStatusOK(opCtx->recoveryUnit()->majorityCommittedSnapshotAvailable());
-    }
-
-    opCtx->setExhaust(cursorPin->queryOptions() & QueryOption_Exhaust);
-
-    if (cursorPin->getExecutor()->lockPolicy() == PlanExecutor::LockPolicy::kLocksInternally) {
-        if (!nss.isCollectionlessCursorNamespace()) {
-            AutoGetDb autoDb(opCtx, nss.db(), MODE_IS);
-            statsTracker.emplace(opCtx,
-                                 nss,
-                                 Top::LockType::NotLocked,
-                                 AutoStatsTracker::LogMode::kUpdateTopAndCurOp,
-                                 CollectionCatalog::get(opCtx)->getDatabaseProfileLevel(nss.db()));
-            auto view =
-                autoDb.getDb() ? ViewCatalog::get(autoDb.getDb())->lookup(opCtx, nss) : nullptr;
-            uassert(
-                ErrorCodes::CommandNotSupportedOnView,
-                str::stream() << "Namespace " << nss.ns()
-                              << " is a view. OP_GET_MORE operations are not supported on views. "
-                              << "Only clients which support the getMore command can be used to "
-                                 "query views.",
-                !view);
-        }
-    } else {
-        readLock.emplace(opCtx, nss);
-        statsTracker.emplace(opCtx,
-                             nss,
-                             Top::LockType::ReadLocked,
-                             AutoStatsTracker::LogMode::kUpdateTopAndCurOp,
-                             CollectionCatalog::get(opCtx)->getDatabaseProfileLevel(nss.db()));
-
-        // This checks to make sure the operation is allowed on a replicated node.  Since we are not
-        // passing in a query object (necessary to check SlaveOK query option), we allow reads
-        // whether we are PRIMARY or SECONDARY.
-        uassertStatusOK(
-            repl::ReplicationCoordinator::get(opCtx)->checkCanServeReadsFor(opCtx, nss, true));
-    }
-
-    std::uint64_t numResults = 0;
-    int startingResult = 0;
-    ResourceConsumption::DocumentUnitCounter docUnitsReturned;
-
-    const int initialBufSize =
-        512 + sizeof(QueryResult::Value) + FindCommon::kMaxBytesToReturnToClientAtOnce;
-
-    BufBuilder bb(initialBufSize);
-    bb.skip(sizeof(QueryResult::Value));
-
-    // Check for spoofing of the ns such that it does not match the one originally there for the
-    // cursor.
-    uassert(ErrorCodes::Unauthorized,
-            str::stream() << "Requested getMore on namespace " << ns << ", but cursor " << cursorid
-                          << " belongs to namespace " << cursorPin->nss().ns(),
-            nss == cursorPin->nss());
-
-    // A user can only call getMore on their own cursor. If there were multiple users authenticated
-    // when the cursor was created, then at least one of them must be authenticated in order to run
-    // getMore on the cursor.
-    uassert(ErrorCodes::Unauthorized,
-            str::stream() << "cursor id " << cursorid
-                          << " was not created by the authenticated user",
-            AuthorizationSession::get(opCtx->getClient())
-                ->isCoauthorizedWith(cursorPin->getAuthenticatedUsers()));
-
-    *isCursorAuthorized = true;
-
-    // Only used by the failpoints.
-    std::function<void()> dropAndReaquireReadLock = [&] {
-        // Make sure an interrupted operation does not prevent us from reacquiring the lock.
-        UninterruptibleLockGuard noInterrupt(opCtx->lockState());
-
-        readLock.reset();
-        readLock.emplace(opCtx, nss);
-    };
-
-    // On early return, get rid of the cursor.
-    auto cursorFreer = makeGuard([&] { cursorPin.deleteUnderlying(); });
-
-    // If the 'waitAfterPinningCursorBeforeGetMoreBatch' fail point is enabled, set the
-    // 'msg' field of this operation's CurOp to signal that we've hit this point and then
-    // repeatedly release and re-acquire the collection readLock at regular intervals until
-    // the failpoint is released. This is done in order to avoid deadlocks caused by the
-    // pinned-cursor failpoints in this file (see SERVER-21997).
-    waitAfterPinningCursorBeforeGetMoreBatch.execute([&](const BSONObj& data) {
-        if (data["shouldNotdropLock"].booleanSafe()) {
-            dropAndReaquireReadLock = []() {};
-        }
-
-        CurOpFailpointHelpers::waitWhileFailPointEnabled(&waitAfterPinningCursorBeforeGetMoreBatch,
-                                                         opCtx,
-                                                         "waitAfterPinningCursorBeforeGetMoreBatch",
-                                                         dropAndReaquireReadLock,
-                                                         nss);
-    });
-
-    uassert(40548,
-            "OP_GET_MORE operations are not supported on tailable aggregations. Only clients "
-            "which support the getMore command can be used on tailable aggregations.",
-            readLock || !cursorPin->isAwaitData());
-    uassert(
-        31124,
-        str::stream()
-            << "OP_GET_MORE does not support cursors with a write concern other than the default."
-               " Use the getMore command instead. Write concern was: "
-            << cursorPin->getWriteConcernOptions().toBSON(),
-        cursorPin->getWriteConcernOptions().isImplicitDefaultWriteConcern());
-
-    // If the operation that spawned this cursor had a time limit set, apply leftover time to this
-    // getmore.
-    if (cursorPin->getLeftoverMaxTimeMicros() < Microseconds::max()) {
-        uassert(40136,
-                "Illegal attempt to set operation deadline within DBDirectClient",
-                !opCtx->getClient()->isInDirectClient());
-        opCtx->setDeadlineAfterNowBy(cursorPin->getLeftoverMaxTimeMicros(),
-                                     ErrorCodes::MaxTimeMSExpired);
-    }
-    opCtx->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.
-
-    // What number result are we starting at?  Used to fill out the reply.
-    startingResult = cursorPin->nReturnedSoFar();
-
-    uint64_t notifierVersion = 0;
-    std::shared_ptr<CappedInsertNotifier> notifier;
-    if (cursorPin->isAwaitData()) {
-        invariant(readLock->getCollection()->isCapped());
-        // Retrieve the notifier which we will wait on until new data arrives. We make sure to do
-        // this in the lock because once we drop the lock it is possible for the collection to
-        // become invalid. The notifier itself will outlive the collection if the collection is
-        // dropped, as we keep a shared_ptr to it.
-        notifier = readLock->getCollection()->getCappedInsertNotifier();
-
-        // Must get the version before we call generateBatch in case a write comes in after that
-        // call and before we call wait on the notifier.
-        notifierVersion = notifier->getVersion();
-    }
-
-    PlanExecutor* exec = cursorPin->getExecutor();
-    exec->reattachToOperationContext(opCtx);
-    exec->restoreState(readLock ? &readLock->getCollection() : nullptr);
-
-    auto planSummary = exec->getPlanExplainer().getPlanSummary();
-    {
-        stdx::lock_guard<Client> lk(*opCtx->getClient());
-        curOp.setPlanSummary_inlock(planSummary);
-
-        // Ensure that the original query object is available in the slow query log, profiler and
-        // currentOp. Upconvert _query to resemble a getMore command, and set the original command
-        // or upconverted legacy query in the originatingCommand field.
-        curOp.setOpDescription_inlock(upconvertGetMoreEntry(nss, cursorid, ntoreturn));
-        curOp.setOriginatingCommand_inlock(cursorPin->getOriginatingCommandObj());
-        // Update the generic cursor in curOp.
-        curOp.setGenericCursor_inlock(cursorPin->toGenericCursor());
-    }
-
-    // If the 'failGetMoreAfterCursorCheckout' failpoint is enabled, throw an exception with the
-    // specified 'errorCode' value, or ErrorCodes::InternalError if 'errorCode' is omitted.
-    failGetMoreAfterCursorCheckout.executeIf(
-        [](const BSONObj& data) {
-            auto errorCode = (data["errorCode"] ? data["errorCode"].safeNumberLong()
-                                                : ErrorCodes::InternalError);
-            uasserted(errorCode, "Hit the 'failGetMoreAfterCursorCheckout' failpoint");
-        },
-        [&opCtx, &nss](const BSONObj& data) {
-            auto dataForFailCommand =
-                data.addField(BSON("failCommands" << BSON_ARRAY("getMore")).firstElement());
-            auto* getMoreCommand = CommandHelpers::findCommand("getMore");
-            return CommandHelpers::shouldActivateFailCommandFailPoint(
-                dataForFailCommand, nss, getMoreCommand, opCtx->getClient());
-        });
-
-    PlanExecutor::ExecState state;
-
-    // We report keysExamined and docsExamined to OpDebug for a given getMore operation. To obtain
-    // these values we need to take a diff of the pre-execution and post-execution metrics, as they
-    // accumulate over the course of a cursor's lifetime.
-    PlanSummaryStats preExecutionStats;
-    exec->getPlanExplainer().getSummaryStats(&preExecutionStats);
-    if (MONGO_unlikely(waitWithPinnedCursorDuringGetMoreBatch.shouldFail())) {
-        CurOpFailpointHelpers::waitWhileFailPointEnabled(&waitWithPinnedCursorDuringGetMoreBatch,
-                                                         opCtx,
-                                                         "waitWithPinnedCursorDuringGetMoreBatch",
-                                                         nullptr);
-    }
-
-    generateBatch(ntoreturn, cursorPin.getCursor(), &bb, &numResults, &docUnitsReturned, &state);
-
-    // If this is an await data cursor, and we hit EOF without generating any results, then we block
-    // waiting for new data to arrive.
-    if (cursorPin->isAwaitData() && state == PlanExecutor::IS_EOF && numResults == 0) {
-        // Save the PlanExecutor and drop our locks.
-        exec->saveState();
-        readLock.reset();
-
-        // Block waiting for data for up to 1 second. Time spent blocking is not counted towards the
-        // total operation latency.
-        curOp.pauseTimer();
-        Seconds timeout(1);
-        notifier->waitUntil(notifierVersion,
-                            opCtx->getServiceContext()->getPreciseClockSource()->now() + timeout);
-        notifier.reset();
-        curOp.resumeTimer();
-
-        // Reacquiring locks.
-        readLock.emplace(opCtx, nss);
-        exec->restoreState(&readLock->getCollection());
-
-        // We woke up because either the timed_wait expired, or there was more data. Either way,
-        // attempt to generate another batch of results.
-        generateBatch(
-            ntoreturn, cursorPin.getCursor(), &bb, &numResults, &docUnitsReturned, &state);
-    }
-
-    PlanSummaryStats postExecutionStats;
-    auto&& explainer = exec->getPlanExplainer();
-    explainer.getSummaryStats(&postExecutionStats);
-    postExecutionStats.totalKeysExamined -= preExecutionStats.totalKeysExamined;
-    postExecutionStats.totalDocsExamined -= preExecutionStats.totalDocsExamined;
-    curOp.debug().setPlanSummaryMetrics(postExecutionStats);
-
-    // We do not report 'execStats' for aggregation or other cursors with the 'kLocksInternally'
-    // policy, both in the original request and subsequent getMore. It would be useful to have this
-    // info for an aggregation, but the source PlanExecutor could be destroyed before we know if we
-    // need 'execStats' and we do not want to generate the stats eagerly for all operations due to
-    // cost.
-    if (cursorPin->getExecutor()->lockPolicy() != PlanExecutor::LockPolicy::kLocksInternally &&
-        curOp.shouldDBProfile(opCtx)) {
-        auto&& [stats, _] = explainer.getWinningPlanStats(ExplainOptions::Verbosity::kExecStats);
-
-        curOp.debug().execStats = std::move(stats);
-    }
-
-    // Our two possible ClientCursorPin cleanup paths are:
-    // 1) If the cursor is not going to be saved, we call deleteUnderlying() on the pin.
-    // 2) If the cursor is going to be saved, we simply let the pin go out of scope. In this case,
-    // the pin's destructor will be invoked, which will call release() on the pin.  Because our
-    // ClientCursorPin is declared after our lock is declared, this will happen under the lock if
-    // any locking was necessary.
-    if (!shouldSaveCursorGetMore(exec, cursorPin->isTailable())) {
-        // cc is now invalid, as is the executor
-        cursorid = 0;
-        curOp.debug().cursorExhausted = true;
-
-        LOGV2_DEBUG(20910,
-                    5,
-                    "getMore NOT saving client cursor",
-                    "planExecutorState"_attr = PlanExecutor::stateToStr(state));
-    } else {
-        cursorFreer.dismiss();
-        // Continue caching the ClientCursor.
-        cursorPin->incNReturnedSoFar(numResults);
-        cursorPin->incNBatches();
-        exec->saveState();
-        exec->detachFromOperationContext();
-        LOGV2_DEBUG(20911,
-                    5,
-                    "getMore saving client cursor",
-                    "planExecutorState"_attr = PlanExecutor::stateToStr(state));
-
-        // Set 'exhaust' if the client requested exhaust and the cursor is not exhausted.
-        *exhaust = opCtx->isExhaust();
-
-        // We assume that cursors created through a DBDirectClient are always used from their
-        // original OperationContext, so we do not need to move time to and from the cursor.
-        if (!opCtx->getClient()->isInDirectClient()) {
-            // If the getmore had a time limit, remaining time is "rolled over" back to the cursor
-            // (for use by future getmore ops).
-            cursorPin->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
-        }
-    }
-
-    // We're about to unpin or delete the cursor as the ClientCursorPin goes out of scope.
-    // If the 'waitBeforeUnpinningOrDeletingCursorAfterGetMoreBatch' failpoint is active, we
-    // set the 'msg' field of this operation's CurOp to signal that we've hit this point and
-    // then spin until the failpoint is released.
-    if (MONGO_unlikely(waitBeforeUnpinningOrDeletingCursorAfterGetMoreBatch.shouldFail())) {
-        CurOpFailpointHelpers::waitWhileFailPointEnabled(
-            &waitBeforeUnpinningOrDeletingCursorAfterGetMoreBatch,
-            opCtx,
-            "waitBeforeUnpinningOrDeletingCursorAfterGetMoreBatch",
-            dropAndReaquireReadLock);
-    }
-
-    // Increment this metric once the command succeeds and we know it will return documents.
-    auto& metricsCollector = ResourceConsumption::MetricsCollector::get(opCtx);
-    metricsCollector.incrementDocUnitsReturned(docUnitsReturned);
-
-    QueryResult::View qr = bb.buf();
-    qr.msgdata().setLen(bb.len());
-    qr.msgdata().setOperation(opReply);
-    qr.setResultFlags(resultFlags);
-    qr.setCursorId(cursorid);
-    qr.setStartingFrom(startingResult);
-    qr.setNReturned(numResults);
-    LOGV2_DEBUG(20912, 5, "getMore returned results", "numResults"_attr = numResults);
-    return Message(bb.release());
-}
-
-bool runQuery(OperationContext* opCtx,
-              QueryMessage& q,
-              const NamespaceString& nss,
-              Message& result) {
-    CurOp& curOp = *CurOp::get(opCtx);
-    curOp.ensureStarted();
-
-    uassert(ErrorCodes::InvalidNamespace,
-            str::stream() << "Invalid ns [" << nss.ns() << "]",
-            nss.isValid());
-    invariant(!nss.isCommand());
-
-    ResourceConsumption::ScopedMetricsCollector scopedMetrics(opCtx, nss.db().toString());
-
-    // Set CurOp information.
-    const auto upconvertedQuery = upconvertQueryEntry(q.query, nss, q.ntoreturn, q.ntoskip);
-
-    // Extract the 'comment' parameter from the upconverted query, if it exists.
-    if (auto commentField = upconvertedQuery["comment"]) {
-        opCtx->setComment(commentField.wrap());
-    }
-
-    beginQueryOp(opCtx, nss, upconvertedQuery, q.ntoreturn, q.ntoskip);
-
-    // Parse the qm into a CanonicalQuery.
-    const boost::intrusive_ptr<ExpressionContext> expCtx =
-        make_intrusive<ExpressionContext>(opCtx, nullptr /* collator */, nss);
-    auto cq = uassertStatusOKWithContext(
-        CanonicalQuery::canonicalize(opCtx,
-                                     q,
-                                     expCtx,
-                                     ExtensionsCallbackReal(opCtx, &nss),
-                                     MatchExpressionParser::kAllowAllSpecialFeatures),
-        "Can't canonicalize query");
-    invariant(cq.get());
-
-    LOGV2_DEBUG(20913, 5, "Running query", "query"_attr = redact(cq->toString()));
-    LOGV2_DEBUG(20914, 2, "Running query", "query"_attr = redact(cq->toStringShort()));
-
-    // Parse, canonicalize, plan, transcribe, and get a plan executor.
-    AutoGetCollectionForReadCommandMaybeLockFree collection(
-        opCtx, nss, AutoGetCollectionViewMode::kViewsForbidden);
-
-    const bool isExhaust = (q.queryOptions & QueryOption_Exhaust) != 0;
-    opCtx->setExhaust(isExhaust);
-
-    {
-        // Allow the query to run on secondaries if the read preference permits it. If no read
-        // preference was specified, allow the query to run iff slaveOk has been set.
-        const bool isSecondaryOk = (q.queryOptions & QueryOption_SecondaryOk) != 0;
-        const bool hasReadPref = q.query.hasField(query_request_helper::kWrappedReadPrefField);
-        const bool secondaryOk = hasReadPref
-            ? uassertStatusOK(ReadPreferenceSetting::fromContainingBSON(q.query))
-                  .canRunOnSecondary()
-            : isSecondaryOk;
-        uassertStatusOK(repl::ReplicationCoordinator::get(opCtx)->checkCanServeReadsFor(
-            opCtx, nss, secondaryOk));
-    }
-
-    const FindCommandRequest& findCommand = cq->getFindCommandRequest();
-    // Get the execution plan for the query.
-    constexpr auto verbosity = ExplainOptions::Verbosity::kExecAllPlans;
-    const bool isExplain = cq->getExplain();
-    expCtx->explain = isExplain ? boost::make_optional(verbosity) : boost::none;
-    auto exec =
-        uassertStatusOK(getExecutorLegacyFind(opCtx, &collection.getCollection(), std::move(cq)));
-
-    // If it's actually an explain, do the explain and return rather than falling through
-    // to the normal query execution loop.
-    if (isExplain) {
-        BufBuilder bb;
-        bb.skip(sizeof(QueryResult::Value));
-
-        BSONObjBuilder explainBob;
-        Explain::explainStages(exec.get(),
-                               collection.getCollection(),
-                               verbosity,
-                               BSONObj(),
-                               upconvertedQuery,
-                               &explainBob);
-
-        // Add the resulting object to the return buffer.
-        BSONObj explainObj = explainBob.obj();
-        bb.appendBuf((void*)explainObj.objdata(), explainObj.objsize());
-
-        // Set query result fields.
-        QueryResult::View qr = bb.buf();
-        qr.setResultFlagsToOk();
-        qr.msgdata().setLen(bb.len());
-        curOp.debug().responseLength = bb.len();
-        qr.msgdata().setOperation(opReply);
-        qr.setCursorId(0);
-        qr.setStartingFrom(0);
-        qr.setNReturned(1);
-        result.setData(bb.release());
-        return false;
-    }
-
-    int maxTimeMS = findCommand.getMaxTimeMS() ? static_cast<int>(*findCommand.getMaxTimeMS()) : 0;
-    // Handle query option $maxTimeMS (not used with commands).
-    if (maxTimeMS > 0) {
-        uassert(40116,
-                "Illegal attempt to set operation deadline within DBDirectClient",
-                !opCtx->getClient()->isInDirectClient());
-        opCtx->setDeadlineAfterNowBy(Milliseconds{maxTimeMS}, ErrorCodes::MaxTimeMSExpired);
-    }
-    opCtx->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.
-
-    FindCommon::waitInFindBeforeMakingBatch(opCtx, *exec->getCanonicalQuery());
-
-    // Run the query.
-    // bb is used to hold query results
-    // this buffer should contain either requested documents per query or
-    // explain information, but not both
-    BufBuilder bb(FindCommon::kInitReplyBufferSize);
-    bb.skip(sizeof(QueryResult::Value));
-
-    // How many results have we obtained from the executor?
-    int numResults = 0;
-    ResourceConsumption::DocumentUnitCounter docUnitsReturned;
-
-    BSONObj obj;
-    PlanExecutor::ExecState state;
-
-    // Get summary info about which plan the executor is using.
-    {
-        stdx::lock_guard<Client> lk(*opCtx->getClient());
-        curOp.setPlanSummary_inlock(exec->getPlanExplainer().getPlanSummary());
-    }
-
-    try {
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
-            // If we can't fit this result inside the current batch, then we stash it for later.
-            if (!FindCommon::haveSpaceForNext(obj, numResults, bb.len())) {
-                exec->enqueue(obj);
-                break;
-            }
-
-            // Add result to output buffer.
-            bb.appendBuf((void*)obj.objdata(), obj.objsize());
-
-            // Count the result.
-            ++numResults;
-
-            docUnitsReturned.observeOne(obj.objsize());
-
-            if (FindCommon::enoughForFirstBatch(findCommand, numResults)) {
-                LOGV2_DEBUG(20915,
-                            5,
-                            "Enough for first batch",
-                            "wantMore"_attr = !findCommand.getSingleBatch(),
-                            "numToReturn"_attr = findCommand.getNtoreturn().value_or(0),
-                            "numResults"_attr = numResults);
-                break;
-            }
-        }
-    } catch (DBException& exception) {
-        auto&& explainer = exec->getPlanExplainer();
-        auto&& [stats, _] = explainer.getWinningPlanStats(ExplainOptions::Verbosity::kExecStats);
-        LOGV2_ERROR(20919,
-                    "Plan executor error during find",
-                    "error"_attr = redact(exception.toStatus()),
-                    "stats"_attr = redact(stats));
-
-        exception.addContext("Executor error during find");
-        throw;
-    }
-
-    // Fill out CurOp based on query results. If we have a cursorid, we will fill out CurOp with
-    // this cursorid later.
-    long long ccId = 0;
-
-    if (shouldSaveCursor(opCtx, collection.getCollection(), state, exec.get())) {
-        // We won't use the executor until it's getMore'd.
-        exec->saveState();
-        exec->detachFromOperationContext();
-
-        const auto& readConcernArgs = repl::ReadConcernArgs::get(opCtx);
-        // Allocate a new ClientCursor and register it with the cursor manager.
-        ClientCursorPin pinnedCursor = CursorManager::get(opCtx)->registerCursor(
-            opCtx,
-            {std::move(exec),
-             nss,
-             AuthorizationSession::get(opCtx->getClient())->getAuthenticatedUserNames(),
-             APIParameters::get(opCtx),
-             opCtx->getWriteConcern(),
-             readConcernArgs,
-             upconvertedQuery,
-             {Privilege(ResourcePattern::forExactNamespace(nss), ActionType::find)}});
-        ccId = pinnedCursor.getCursor()->cursorid();
-
-        LOGV2_DEBUG(20916,
-                    5,
-                    "Caching executor after returning results",
-                    "cursorId"_attr = ccId,
-                    "numResults"_attr = numResults);
-
-        // Set curOp.debug().exhaust if the client requested exhaust and the cursor is not
-        // exhausted.
-        if (opCtx->isExhaust()) {
-            curOp.debug().exhaust = true;
-        }
-
-        pinnedCursor.getCursor()->setNReturnedSoFar(numResults);
-        pinnedCursor.getCursor()->incNBatches();
-
-        // We assume that cursors created through a DBDirectClient are always used from their
-        // original OperationContext, so we do not need to move time to and from the cursor.
-        if (!opCtx->getClient()->isInDirectClient()) {
-            // If the query had a time limit, remaining time is "rolled over" to the cursor (for
-            // use by future getmore ops).
-            pinnedCursor.getCursor()->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
-        }
-
-        endQueryOp(opCtx,
-                   collection.getCollection(),
-                   *pinnedCursor.getCursor()->getExecutor(),
-                   numResults,
-                   ccId);
-    } else {
-        LOGV2_DEBUG(
-            20917, 5, "Not caching executor but returning results", "numResults"_attr = numResults);
-        endQueryOp(opCtx, collection.getCollection(), *exec, numResults, ccId);
-    }
-
-    // Increment this metric once it has succeeded and we know it will return documents.
-    auto& metricsCollector = ResourceConsumption::MetricsCollector::get(opCtx);
-    metricsCollector.incrementDocUnitsReturned(docUnitsReturned);
-
-    // Fill out the output buffer's header.
-    QueryResult::View queryResultView = bb.buf();
-    queryResultView.setCursorId(ccId);
-    queryResultView.setResultFlagsToOk();
-    queryResultView.msgdata().setLen(bb.len());
-    queryResultView.msgdata().setOperation(opReply);
-    queryResultView.setStartingFrom(0);
-    queryResultView.setNReturned(numResults);
-
-    // Add the results from the query into the output buffer.
-    result.setData(bb.release());
-
-    // curOp.debug().exhaust is set above if the client requested exhaust and the cursor is not
-    // exhausted.
-    return curOp.debug().exhaust;
-}
-
 }  // namespace mongo