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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.
*/
#pragma once
#include "mongo/bson/bsonobj.h"
#include "mongo/db/exec/plan_stats.h"
#include "mongo/db/query/classic_plan_cache.h"
#include "mongo/db/query/explain_options.h"
#include "mongo/db/query/plan_enumerator_explain_info.h"
#include "mongo/db/query/plan_summary_stats.h"
#include "mongo/db/query/query_solution.h"
#include "mongo/util/duration.h"
namespace mongo {
/**
* This interface defines an API to provide information on the execution plans generated by the
* query planner for a user query in various formats.
*/
class PlanExplainer {
public:
/**
* A version of the explain format. "1" is used for the classic engine and "2" for SBE.
*/
using ExplainVersion = std::string;
/**
* This pair holds a serialized BSON document that details the plan selected by the query
* planner, and optional summary stats for an execution tree if the verbosity level for the
* generated stats is 'executionStats' or higher. The format of these stats are opaque to the
* caller, and different implementations may choose to provide different stats.
*/
using PlanStatsDetails = std::pair<BSONObj, boost::optional<PlanSummaryStats>>;
PlanExplainer() {}
PlanExplainer(const QuerySolution* solution)
: _enumeratorExplainInfo{solution ? solution->_enumeratorExplainInfo
: PlanEnumeratorExplainInfo{}} {}
PlanExplainer(const PlanEnumeratorExplainInfo& info) : _enumeratorExplainInfo{info} {}
virtual ~PlanExplainer() = default;
/**
* Returns a version of the explain format supported by this explainer.
*/
virtual const ExplainVersion& getVersion() const = 0;
/**
* Returns 'true' if this PlanExplainer can provide information on the winning plan and rejected
* candidate plans, meaning that the QueryPlanner generated multiple candidate plans and the
* winning plan was chosen by the multi-planner.
*/
virtual bool isMultiPlan() const = 0;
/**
* Returns a short string, suitable for the logs, which summarizes the execution plan.
*/
virtual std::string getPlanSummary() const = 0;
/**
* Fills out 'statsOut' with summary stats collected during the execution of the underlying
* plan. This is a lightweight alternative which is useful when operations want to request a
* summary of the available debug information without generating complete explain output.
*
* The summary stats are consumed by debug mechanisms such as the profiler and the slow query
* log.
*/
virtual void getSummaryStats(PlanSummaryStats* statsOut) const = 0;
/**
* Fills out 'statsOut' for the secondary collection 'secondaryColl'. Subclasses may
* override this function if the summary stats for secondary collections need to be reported
* separately.
*/
virtual void getSecondarySummaryStats(std::string secondaryColl,
PlanSummaryStats* statsOut) const {}
/**
* Returns statistics that detail the winning plan selected by the multi-planner, or, if no
* multi-planning has been performed, for the single plan selected by the QueryPlanner.
*
* The 'verbosity' level parameter determines the amount of information to be returned.
*/
virtual PlanStatsDetails getWinningPlanStats(ExplainOptions::Verbosity verbosity) const = 0;
/**
* Returns statistics for the trial period of the winning plan selected by the multi-planner.
*/
virtual PlanStatsDetails getWinningPlanTrialStats() const = 0;
/**
* Returns statistics that detail candidate plans rejected by the multi-planner. If no
* multi-planning has been performed, an empty vector is returned.
*
* The 'verbosity' level parameter determines the amount of information to be returned.
*/
virtual std::vector<PlanStatsDetails> getRejectedPlansStats(
ExplainOptions::Verbosity verbosity) const = 0;
/**
* Returns an object containing what query knobs the planner hit during plan enumeration.
*/
PlanEnumeratorExplainInfo getEnumeratorInfo() const {
return _enumeratorExplainInfo;
}
void updateEnumeratorExplainInfo(const PlanEnumeratorExplainInfo& other) {
_enumeratorExplainInfo.merge(other);
}
protected:
PlanEnumeratorExplainInfo _enumeratorExplainInfo;
};
} // namespace mongo
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