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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 "mongo/util/duration.h"
#include <boost/optional.hpp>
#include <queue>
#include "mongo/db/concurrency/exception_util.h"
#include "mongo/db/exec/multi_plan.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/query/plan_executor.h"
#include "mongo/db/query/query_solution.h"
#include "mongo/db/shard_role.h"
namespace mongo {
/**
* Query execution helper. Runs the argument function 'f'. If 'f' throws an exception other than
* 'WriteConflictException' or 'TemporarilyUnavailableException', then these exceptions escape
* this function. In contrast 'WriteConflictException' or 'TemporarilyUnavailableException' are
* caught, the given 'yieldHandler' is run, and the helper returns PlanStage::NEED_YIELD.
*
* In a multi-document transaction, it rethrows a TemporarilyUnavailableException as a
* WriteConflictException.
*/
template <typename F, typename H>
auto handlePlanStageYield(
ExpressionContext* expCtx, StringData opStr, StringData ns, F&& f, H&& yieldHandler) {
auto opCtx = expCtx->opCtx;
invariant(opCtx);
invariant(opCtx->lockState());
invariant(opCtx->recoveryUnit());
invariant(!expCtx->getTemporarilyUnavailableException());
try {
return f();
} catch (const WriteConflictException&) {
yieldHandler();
return PlanStage::NEED_YIELD;
} catch (const TemporarilyUnavailableException& e) {
if (opCtx->inMultiDocumentTransaction()) {
handleTemporarilyUnavailableExceptionInTransaction(opCtx, opStr, ns, e);
}
expCtx->setTemporarilyUnavailableException(true);
yieldHandler();
return PlanStage::NEED_YIELD;
}
}
class CappedInsertNotifier;
class CollectionScan;
struct CappedInsertNotifierData;
class PlanExecutorImpl : public PlanExecutor {
PlanExecutorImpl(const PlanExecutorImpl&) = delete;
PlanExecutorImpl& operator=(const PlanExecutorImpl&) = delete;
public:
/**
* Callers should obtain PlanExecutorImpl instances uses the 'plan_executor_factory' methods, in
* order to avoid depending directly on this concrete implementation of the PlanExecutor
* interface.
*/
PlanExecutorImpl(OperationContext* opCtx,
std::unique_ptr<WorkingSet> ws,
std::unique_ptr<PlanStage> rt,
std::unique_ptr<QuerySolution> qs,
std::unique_ptr<CanonicalQuery> cq,
const boost::intrusive_ptr<ExpressionContext>& expCtx,
VariantCollectionPtrOrAcquisition collection,
bool returnOwnedBson,
NamespaceString nss,
PlanYieldPolicy::YieldPolicy yieldPolicy);
virtual ~PlanExecutorImpl();
CanonicalQuery* getCanonicalQuery() const final;
const NamespaceString& nss() const final;
const std::vector<NamespaceStringOrUUID>& getSecondaryNamespaces() const final;
OperationContext* getOpCtx() const final;
void saveState() final;
void restoreState(const RestoreContext& context) final;
void detachFromOperationContext() final;
void reattachToOperationContext(OperationContext* opCtx) final;
ExecState getNextDocument(Document* objOut, RecordId* dlOut) final;
ExecState getNext(BSONObj* out, RecordId* dlOut) final;
bool isEOF() final;
long long executeCount() override;
UpdateResult executeUpdate() override;
UpdateResult getUpdateResult() const override;
long long executeDelete() override;
BatchedDeleteStats getBatchedDeleteStats() override;
void markAsKilled(Status killStatus) final;
void dispose(OperationContext* opCtx) final;
void stashResult(const BSONObj& obj) final;
bool isMarkedAsKilled() const final;
Status getKillStatus() final;
bool isDisposed() const final;
Timestamp getLatestOplogTimestamp() const final;
BSONObj getPostBatchResumeToken() const final;
LockPolicy lockPolicy() const final;
const PlanExplainer& getPlanExplainer() const final;
PlanExecutor::QueryFramework getQueryFramework() const override final {
return PlanExecutor::QueryFramework::kClassicOnly;
}
/**
* Same as restoreState() but without the logic to retry if a WriteConflictException is thrown.
*
* This is only public for PlanYieldPolicy. DO NOT CALL ANYWHERE ELSE.
*/
void restoreStateWithoutRetrying(const RestoreContext& context, const Yieldable* yieldable);
/**
* Return a pointer to this executor's MultiPlanStage, or nullptr if it does not have one.
*/
MultiPlanStage* getMultiPlanStage() const;
PlanStage* getRootStage() const;
void enableSaveRecoveryUnitAcrossCommandsIfSupported() override {}
bool isSaveRecoveryUnitAcrossCommandsEnabled() const override {
return false;
}
void setReturnOwnedData(bool returnOwnedData) override final {
_mustReturnOwnedBson = returnOwnedData;
}
private:
/**
* Executes the underlying PlanStage tree until it indicates EOF. Throws an exception if the
* plan results in an error.
*
* Useful for cases where the caller wishes to execute the plan and extract stats from it (e.g.
* the result of a count or update) rather than returning a set of resulting documents.
*/
void _executePlan();
/**
* Called on construction in order to ensure that when callers receive a new instance of a
* 'PlanExecutorImpl', plan selection has already been completed.
*
* 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();
ExecState _getNextImpl(Snapshotted<Document>* objOut, RecordId* dlOut);
// The OperationContext that we're executing within. This can be updated if necessary by using
// detachFromOperationContext() and reattachToOperationContext().
OperationContext* _opCtx;
// Note, this can be null. Some queries don't need a CanonicalQuery for planning. For example,
// aggregation queries create a PlanExecutor with no CanonicalQuery.
std::unique_ptr<CanonicalQuery> _cq;
// When '_cq' is not null, this will point to the same ExpressionContext that is in the '_cq'
// object. Note that this pointer can also be null when '_cq' is null. For example a "list
// collections" query does not need a CanonicalQuery or ExpressionContext.
boost::intrusive_ptr<ExpressionContext> _expCtx;
std::unique_ptr<WorkingSet> _workingSet;
std::unique_ptr<QuerySolution> _qs;
std::unique_ptr<PlanStage> _root;
std::unique_ptr<PlanExplainer> _planExplainer;
// 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();
// Whether the executor must return owned BSON.
bool _mustReturnOwnedBson;
// What namespace are we operating over?
NamespaceString _nss;
// This is used to handle automatic yielding when allowed by the YieldPolicy. Never nullptr.
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::deque<Document> _stash;
// The output document that is used by getNext BSON API. This allows us to avoid constantly
// allocating and freeing DocumentStorage.
Document _docOutput;
enum { kUsable, kSaved, kDetached, kDisposed } _currentState = kUsable;
// A pointer either to a CollectionScan stage, if present in the execution tree, or nullptr
// otherwise. We cache it to avoid the need to traverse the execution tree in runtime when the
// executor is requested to return the oplog tracking info. Since this info is provided by
// either of these stages, the executor will simply delegate the request to the cached stage.
const CollectionScan* _collScanStage{nullptr};
};
} // namespace mongo
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