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/**
* Copyright (C) 2020-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/query/sbe_runtime_planner.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/exec/sbe/expressions/expression.h"
#include "mongo/db/exec/trial_period_utils.h"
#include "mongo/db/query/plan_executor_sbe.h"
namespace mongo::sbe {
namespace {
/**
* Fetches a next document form the given plan stage tree and returns 'true' if the plan stage
* returns EOF, or throws 'TrialRunProgressTracker::EarlyExitException' exception. Otherwise, the
* loaded document is placed into the candidate's plan result queue.
*
* If the plan stage throws a 'QueryExceededMemoryLimitNoDiskUseAllowed', it will be caught and the
* 'candidate->failed' flag will be set to 'true', and the 'numFailures' parameter incremented by 1.
* This failure is considered recoverable, as another candidate plan may require less memory, or may
* not contain a stage requiring spilling to disk at all.
*/
bool fetchNextDocument(plan_ranker::CandidatePlan* candidate,
const std::pair<sbe::value::SlotAccessor*, sbe::value::SlotAccessor*>& slots,
size_t* numFailures) {
try {
BSONObj obj;
RecordId recordId;
auto [resultSlot, recordIdSlot] = slots;
auto state = fetchNext(candidate->root.get(),
resultSlot,
recordIdSlot,
&obj,
recordIdSlot ? &recordId : nullptr);
if (state == sbe::PlanState::IS_EOF) {
candidate->root->close();
return true;
}
invariant(state == sbe::PlanState::ADVANCED);
candidate->results.push({std::move(obj), {recordIdSlot != nullptr, recordId}});
} catch (const ExceptionFor<ErrorCodes::QueryTrialRunCompleted>&) {
candidate->exitedEarly = true;
return true;
} catch (const ExceptionFor<ErrorCodes::QueryExceededMemoryLimitNoDiskUseAllowed>&) {
candidate->root->close();
candidate->failed = true;
++(*numFailures);
}
return false;
}
} // namespace
std::tuple<sbe::value::SlotAccessor*, sbe::value::SlotAccessor*, bool>
BaseRuntimePlanner::prepareExecutionPlan(PlanStage* root,
stage_builder::PlanStageData* data) const {
invariant(root);
invariant(data);
root->prepare(data->ctx);
sbe::value::SlotAccessor* resultSlot{nullptr};
if (auto slot = data->outputs.getIfExists(stage_builder::PlanStageSlots::kResult); slot) {
resultSlot = root->getAccessor(data->ctx, *slot);
uassert(4822871, "Query does not have result slot.", resultSlot);
}
sbe::value::SlotAccessor* recordIdSlot{nullptr};
if (auto slot = data->outputs.getIfExists(stage_builder::PlanStageSlots::kRecordId); slot) {
recordIdSlot = root->getAccessor(data->ctx, *slot);
uassert(4822872, "Query does not have record ID slot.", recordIdSlot);
}
root->attachFromOperationContext(_opCtx);
auto exitedEarly{false};
try {
root->open(false);
} catch (const ExceptionFor<ErrorCodes::QueryTrialRunCompleted>&) {
exitedEarly = true;
}
return {resultSlot, recordIdSlot, exitedEarly};
}
std::vector<plan_ranker::CandidatePlan> BaseRuntimePlanner::collectExecutionStats(
std::vector<std::unique_ptr<QuerySolution>> solutions,
std::vector<std::pair<std::unique_ptr<PlanStage>, stage_builder::PlanStageData>> roots) {
invariant(solutions.size() == roots.size());
std::vector<plan_ranker::CandidatePlan> candidates;
std::vector<std::pair<sbe::value::SlotAccessor*, sbe::value::SlotAccessor*>> slots;
for (size_t ix = 0; ix < roots.size(); ++ix) {
auto&& [root, data] = roots[ix];
auto [resultSlot, recordIdSlot, exitedEarly] = prepareExecutionPlan(root.get(), &data);
candidates.push_back(
{std::move(solutions[ix]), std::move(root), std::move(data), exitedEarly});
slots.push_back({resultSlot, recordIdSlot});
}
auto done{false};
size_t numFailures{0};
const auto maxNumResults{trial_period::getTrialPeriodNumToReturn(_cq)};
for (size_t it = 0; it < maxNumResults && !done; ++it) {
for (size_t ix = 0; ix < candidates.size(); ++ix) {
// Even if we had a candidate plan that exited early, we still want continue the trial
// run as the early exited plan may not be the best. E.g., it could be blocked in a SORT
// stage until one of the trial period metrics was reached, causing the plan to raise an
// early exit exception and return control back to the runtime planner. If that happens,
// we need to continue and complete the trial period for all candidates, as some of them
// may have a better cost.
if (candidates[ix].failed || candidates[ix].exitedEarly) {
continue;
}
done |= fetchNextDocument(&candidates[ix], slots[ix], &numFailures) ||
(numFailures == candidates.size());
}
}
// Make sure we have at least one plan which hasn't failed.
uassert(4822873,
"Runtime planner encountered a failure while collecting execution stats",
numFailures != candidates.size());
return candidates;
}
} // namespace mongo::sbe
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