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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.
*/
#pragma once
#include <boost/optional.hpp>
#include <queue>
#include "mongo/base/disallow_copying.h"
#include "mongo/db/query/plan_executor.h"
namespace mongo {
class PlanExecutorImpl : public PlanExecutor {
MONGO_DISALLOW_COPYING(PlanExecutorImpl);
public:
/**
* Public factory methods delegate to this impl factory to do their work.
*/
static StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> make(
OperationContext* opCtx,
std::unique_ptr<WorkingSet> ws,
std::unique_ptr<PlanStage> rt,
std::unique_ptr<QuerySolution> qs,
std::unique_ptr<CanonicalQuery> cq,
const Collection* collection,
NamespaceString nss,
YieldPolicy yieldPolicy);
virtual ~PlanExecutorImpl();
WorkingSet* getWorkingSet() const final;
PlanStage* getRootStage() const final;
CanonicalQuery* getCanonicalQuery() const final;
const NamespaceString& nss() const final;
OperationContext* getOpCtx() const final;
void saveState() final;
void restoreState() final;
void detachFromOperationContext() final;
void reattachToOperationContext(OperationContext* opCtx) final;
void restoreStateWithoutRetrying() final;
ExecState getNextSnapshotted(Snapshotted<BSONObj>* objOut, RecordId* dlOut) final;
ExecState getNext(BSONObj* objOut, RecordId* dlOut) final;
bool isEOF() final;
Status executePlan() final;
void markAsKilled(Status killStatus) final;
void dispose(OperationContext* opCtx) final;
void enqueue(const BSONObj& obj) final;
BSONObjSet getOutputSorts() const final;
bool isMarkedAsKilled() const final;
Status getKillStatus() final;
bool isDisposed() const final;
bool isDetached() const final;
Timestamp getLatestOplogTimestamp() const final;
BSONObj getPostBatchResumeToken() const final;
Status getMemberObjectStatus(const BSONObj& memberObj) const final;
private:
/**
* New PlanExecutor instances are created with the static make() method above.
*/
PlanExecutorImpl(OperationContext* opCtx,
std::unique_ptr<WorkingSet> ws,
std::unique_ptr<PlanStage> rt,
std::unique_ptr<QuerySolution> qs,
std::unique_ptr<CanonicalQuery> cq,
const Collection* collection,
NamespaceString nss,
YieldPolicy yieldPolicy);
/**
* Clients of PlanExecutor expect that on receiving a new instance from one of the make()
* factory methods, plan selection has already been completed. In order to enforce this
* property, this function is called to do plan selection prior to returning the new
* PlanExecutor.
*
* If the tree contains plan selection stages, such as MultiPlanStage or SubplanStage,
* this calls into their underlying plan selection facilities. Otherwise, does nothing.
*
* If a YIELD_AUTO policy is set then locks are yielded during plan selection.
*
* Returns a non-OK status if query planning fails. In particular, this function returns
* ErrorCodes::QueryPlanKilled if plan execution cannot proceed due to a concurrent write or
* catalog operation.
*/
Status _pickBestPlan();
/**
* Returns true if the PlanExecutor should listen for inserts, which is when a getMore is called
* on a tailable and awaitData cursor that still has time left and hasn't been interrupted.
*/
bool _shouldListenForInserts();
/**
* Returns true if the PlanExecutor should wait for data to be inserted, which is when a getMore
* is called on a tailable and awaitData cursor on a capped collection. Returns false if an EOF
* should be returned immediately.
*/
bool _shouldWaitForInserts();
/**
* Gets the CappedInsertNotifier for a capped collection. Returns nullptr if this plan executor
* is not capable of yielding based on a notifier.
*/
std::shared_ptr<CappedInsertNotifier> _getCappedInsertNotifier();
/**
* Yields locks and waits for inserts to the collection. Returns ADVANCED if there has been an
* insertion and there may be new results. Returns DEAD if the PlanExecutor was killed during a
* yield. This method is only to be used for tailable and awaitData cursors, so rather than
* returning DEAD if the operation has exceeded its time limit, we return IS_EOF to preserve
* this PlanExecutor for future use.
*
* If an error is encountered and 'errorObj' is provided, it is populated with an object
* describing the error.
*/
ExecState _waitForInserts(CappedInsertNotifierData* notifierData,
Snapshotted<BSONObj>* errorObj);
/**
* Common implementation for getNext() and getNextSnapshotted().
*/
ExecState _getNextImpl(Snapshotted<BSONObj>* objOut, RecordId* dlOut);
// The OperationContext that we're executing within. This can be updated if necessary by using
// detachFromOperationContext() and reattachToOperationContext().
OperationContext* _opCtx;
std::unique_ptr<CanonicalQuery> _cq;
std::unique_ptr<WorkingSet> _workingSet;
std::unique_ptr<QuerySolution> _qs;
std::unique_ptr<PlanStage> _root;
// If _killStatus has a non-OK value, then we have been killed and the value represents the
// reason for the kill.
Status _killStatus = Status::OK();
// What namespace are we operating over?
NamespaceString _nss;
// This is used to handle automatic yielding when allowed by the YieldPolicy. Never NULL.
// TODO make this a non-pointer member. This requires some header shuffling so that this
// file includes plan_yield_policy.h rather than the other way around.
const std::unique_ptr<PlanYieldPolicy> _yieldPolicy;
// A stash of results generated by this plan that the user of the PlanExecutor didn't want
// to consume yet. We empty the queue before retrieving further results from the plan
// stages.
std::queue<BSONObj> _stash;
enum { kUsable, kSaved, kDetached, kDisposed } _currentState = kUsable;
bool _everDetachedFromOperationContext = false;
};
} // namespace mongo
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