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/**
* Copyright (C) 2018-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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/platform/basic.h"
#include "mongo/db/exec/trial_stage.h"
#include <algorithm>
#include <memory>
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/exec/or.h"
#include "mongo/db/exec/queued_data_stage.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/logv2/log.h"
namespace mongo {
const char* TrialStage::kStageType = "TRIAL";
TrialStage::TrialStage(OperationContext* opCtx,
WorkingSet* ws,
std::unique_ptr<PlanStage> trialPlan,
std::unique_ptr<PlanStage> backupPlan,
size_t maxTrialWorks,
double minWorkAdvancedRatio)
: PlanStage(kStageType, opCtx), _ws(ws) {
invariant(minWorkAdvancedRatio > 0);
invariant(minWorkAdvancedRatio <= 1);
invariant(maxTrialWorks > 0);
invariant(trialPlan);
invariant(backupPlan);
// Set the trial plan as our only child, and keep the backup plan in reserve.
_children.push_back(std::move(trialPlan));
_backupPlan = std::move(backupPlan);
// We need to cache results during the trial phase in case it succeeds.
_queuedData = std::make_unique<QueuedDataStage>(opCtx, _ws);
// Set up stats tracking specific to this stage.
_specificStats.successThreshold = minWorkAdvancedRatio;
_specificStats.trialPeriodMaxWorks = maxTrialWorks;
}
Status TrialStage::pickBestPlan(PlanYieldPolicy* yieldPolicy) {
// Work the trial plan until the evaluation is complete.
while (!_specificStats.trialCompleted) {
WorkingSetID id = WorkingSet::INVALID_ID;
const bool mustYield = (work(&id) == PlanStage::NEED_YIELD);
if (mustYield || yieldPolicy->shouldYieldOrInterrupt()) {
if (mustYield && !yieldPolicy->canAutoYield()) {
throw WriteConflictException();
}
auto yieldStatus = yieldPolicy->yieldOrInterrupt();
if (!yieldStatus.isOK()) {
return yieldStatus;
}
}
}
return Status::OK();
}
PlanStage::StageState TrialStage::doWork(WorkingSetID* out) {
// Whether or not we have completed the trial phase, we should have exactly one active child.
invariant(_children.size() == 1);
invariant(_children.front());
// If the trial period isn't complete, run through a single step of the trial.
if (!_specificStats.trialCompleted) {
return _workTrialPlan(out);
}
// If we reach this point, the final plan has been set as our only child.
return child()->work(out);
}
PlanStage::StageState TrialStage::_workTrialPlan(WorkingSetID* out) {
// We should never call this method after the trial phase has completed.
invariant(!_specificStats.trialCompleted);
PlanStage::StageState state = child()->work(out);
switch (state) {
case PlanStage::ADVANCED: {
// We need to cache results until the trial is complete. Ensure the BSONObj underlying
// the WorkingSetMember is owned, and set the return state to NEED_TIME so that we do
// not also try to return it.
WorkingSetMember* member = _ws->get(*out);
member->makeObjOwnedIfNeeded();
static_cast<QueuedDataStage*>(_queuedData.get())->pushBack(*out);
*out = WorkingSet::INVALID_ID;
state = NEED_TIME;
// Increment the 'advanced' count and fall through into NEED_TIME so that we check for
// the end of the trial period and assess the results for both NEED_TIME and ADVANCED.
++_specificStats.trialAdvanced;
}
case PlanStage::NEED_TIME:
// Check whether we have completed the evaluation phase.
_specificStats.trialCompleted =
(++_specificStats.trialWorks == _specificStats.trialPeriodMaxWorks);
// If we've reached the end of the trial phase, attempt to build the final plan.
if (_specificStats.trialCompleted) {
_assessTrialAndBuildFinalPlan();
}
return state;
case PlanStage::NEED_YIELD:
// Nothing to update here.
return state;
case PlanStage::IS_EOF:
// EOF always marks the successful end of the trial phase. Swap in the queued data as
// the active plan and return NEED_TIME so that the caller will consume the cache.
_specificStats.trialCompleted = _specificStats.trialSucceeded = true;
_replaceCurrentPlan(_queuedData);
return NEED_TIME;
case PlanStage::FAILURE:
// Either of these cause us to immediately end the trial phase and switch to the backup.
auto statusDoc = WorkingSetCommon::getStatusMemberDocument(*_ws, *out);
BSONObj statusObj = statusDoc ? statusDoc->toBson() : BSONObj();
LOGV2_DEBUG(20604,
1,
"Trial plan failed; switching to backup plan. Status: {statusObj}",
"statusObj"_attr = redact(statusObj));
_specificStats.trialCompleted = true;
_replaceCurrentPlan(_backupPlan);
*out = WorkingSet::INVALID_ID;
return NEED_TIME;
}
MONGO_UNREACHABLE;
}
void TrialStage::_assessTrialAndBuildFinalPlan() {
// We should only ever reach here when the trial period ran to completion.
invariant(_specificStats.trialWorks == _specificStats.trialPeriodMaxWorks);
invariant(_specificStats.trialCompleted);
// If we ADVANCED a sufficient number of times over the trial, then the trial succeeded.
_specificStats.trialSucceeded = _specificStats.trialAdvanced >=
(_specificStats.trialPeriodMaxWorks * _specificStats.successThreshold);
// If the trial failed, all we need do is adopt the backup plan.
if (!_specificStats.trialSucceeded) {
_replaceCurrentPlan(_backupPlan);
return;
}
// The trial plan succeeded, but we need to build a plan that includes the queued data. Create a
// final plan which UNIONs across the QueuedDataStage and the trial plan.
std::unique_ptr<PlanStage> unionPlan =
std::make_unique<OrStage>(getOpCtx(), _ws, false, nullptr);
static_cast<OrStage*>(unionPlan.get())->addChild(std::move(_queuedData));
static_cast<OrStage*>(unionPlan.get())->addChild(std::move(_children.front()));
_replaceCurrentPlan(unionPlan);
}
void TrialStage::_replaceCurrentPlan(std::unique_ptr<PlanStage>& newPlan) {
invariant(_children.size() == 1);
_children.front().swap(newPlan);
}
std::unique_ptr<PlanStageStats> TrialStage::getStats() {
_commonStats.isEOF = isEOF();
auto ret = std::make_unique<PlanStageStats>(_commonStats, STAGE_TRIAL);
ret->specific = std::make_unique<TrialStats>(_specificStats);
ret->children.emplace_back(child()->getStats());
return ret;
}
void TrialStage::doDetachFromOperationContext() {
if (_backupPlan) {
_backupPlan->detachFromOperationContext();
}
if (_queuedData) {
_queuedData->detachFromOperationContext();
}
}
void TrialStage::doReattachToOperationContext() {
if (_backupPlan) {
_backupPlan->reattachToOperationContext(getOpCtx());
}
if (_queuedData) {
_queuedData->reattachToOperationContext(getOpCtx());
}
}
void TrialStage::doDispose() {
if (_backupPlan) {
_backupPlan->dispose(getOpCtx());
}
if (_queuedData) {
_queuedData->dispose(getOpCtx());
}
}
} // namespace mongo
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