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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/db/exec/plan_stage.h"
#include "mongo/db/exec/plan_stats.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/explain_options.h"
#include "mongo/db/query/plan_executor.h"
#include "mongo/db/query/query_planner_params.h"
#include "mongo/db/query/query_solution.h"
namespace mongo {
class Collection;
class OperationContext;
struct PlanSummaryStats;
/**
* Namespace for the collection of static methods used to generate explain information.
*/
class Explain {
public:
/**
* Get explain BSON for the execution stages contained by 'exec'. Use this function if you
* have a PlanExecutor and want to convert it into a human readable explain format. Any
* operation which has a query component (e.g. find, update, group) can be explained via
* this function.
*
* The explain information is extracted from 'exec' and added to the out-parameter 'out'.
*
* The explain information is generated with the level of detail specified by 'verbosity'.
*
* Does not take ownership of its arguments.
*
* The caller should hold at least an IS lock on the collection the that the query runs on,
* even if 'collection' is nullptr.
*
* If there is an error during the execution of the query, the error message and code are
* added to the "executionStats" section of the explain.
*/
static void explainStages(PlanExecutor* exec,
const Collection* collection,
ExplainOptions::Verbosity verbosity,
BSONObjBuilder* out);
/**
* Adds "queryPlanner" and "executionStats" (if requested in verbosity) fields to 'out'. Unlike
* the other overload of explainStages() above, this one does not add the "serverInfo" section.
*
* - 'exec' is the stage tree for the operation being explained.
* - 'collection' is the relevant collection. The caller should hold at least an IS lock on the
* collection which the query ran on, even 'collection' is nullptr.
* - 'verbosity' is the verbosity level of the explain.
* - 'executePlanStatus' is the status returned after executing the query (Status::OK if the
* query wasn't executed).
* - 'winningPlanTrialStats' is the stats of the winning plan during the trial period. May be
* nullptr.
* - 'out' is the builder for the explain output.
**/
static void explainStages(PlanExecutor* exec,
const Collection* collection,
ExplainOptions::Verbosity verbosity,
Status executePlanStatus,
PlanStageStats* winningPlanTrialStats,
BSONObjBuilder* out);
/**
* Gets explain BSON for the document sources contained by 'exec'. Use this function if you
* have a PlanExecutor whose root is a PipelineProxyStage and want to turn it into a human
* readable explain format.
*
* The explain information is generated with the level of detail specified by 'verbosity'.
**/
static void explainPipelineExecutor(PlanExecutor* exec,
ExplainOptions::Verbosity verbosity,
BSONObjBuilder* out);
/**
* Converts the PlanExecutor's winning plan stats tree to BSON and returns to the caller.
*/
static BSONObj getWinningPlanStats(const PlanExecutor* exec);
/**
* Converts the PlanExecutor's winning plan stats tree to BSON and returns the result through
* the out-parameter 'bob'.
*/
static void getWinningPlanStats(const PlanExecutor* exec, BSONObjBuilder* bob);
/**
* Converts the stats tree 'stats' into a corresponding BSON object containing
* explain information.
*
* Generates the BSON stats at a verbosity specified by 'verbosity'. Defaults
* to execution stats verbosity.
*/
static BSONObj statsToBSON(
const PlanStageStats& stats,
ExplainOptions::Verbosity verbosity = ExplainOptions::Verbosity::kExecStats);
/**
* This version of stats tree to BSON conversion returns the result through the
* out-parameter 'bob' rather than returning a BSONObj.
*
* Generates the BSON stats at a verbosity specified by 'verbosity'. Defaults
* to execution stats verbosity.
*/
static void statsToBSON(
const PlanStageStats& stats,
BSONObjBuilder* bob,
ExplainOptions::Verbosity verbosity = ExplainOptions::Verbosity::kExecStats);
/**
* Returns a short plan summary std::string describing the leaves of the query plan.
*/
static std::string getPlanSummary(const PlanExecutor* exec);
static std::string getPlanSummary(const PlanStage* root);
/**
* Fills out 'statsOut' with summary stats using the execution tree contained
* in 'exec'.
*
* The summary stats are consumed by debug mechanisms such as the profiler and
* the slow query log.
*
* This is a lightweight alternative for explainStages(...) above which is useful
* when operations want to request debug information without doing all the work
* to generate a full explain.
*
* Does not take ownership of its arguments.
*/
static void getSummaryStats(const PlanExecutor& exec, PlanSummaryStats* statsOut);
/**
* If exec's root stage is a MultiPlanStage, returns the stats for the trial period of of the
* winning plan. Otherwise, returns nullptr.
*
* Must be called _before_ calling PlanExecutor::executePlan() or PlanExecutor::getNext().
**/
static std::unique_ptr<PlanStageStats> getWinningPlanTrialStats(PlanExecutor* exec);
/**
* Generates the execution stats section for the stats tree 'stats', adding the resulting BSON
* to 'out'.
*
* The 'totalTimeMillis' value passed here will be added to the top level of the execution stats
* section, but will not affect the reporting of timing for individual stages. If
* 'totalTimeMillis' is not set, we use the approximate timing information collected by the
* stages.
*
* Stats are generated at the verbosity specified by 'verbosity'.
**/
static void generateSinglePlanExecutionInfo(const PlanStageStats* stats,
ExplainOptions::Verbosity verbosity,
boost::optional<long long> totalTimeMillis,
BSONObjBuilder* out);
/**
* Serializes a PlanCacheEntry to the provided BSON object builder. The output format is
* intended to be human readable, and useful for debugging query performance problems related to
* the plan cache.
*/
static void planCacheEntryToBSON(const PlanCacheEntry& entry, BSONObjBuilder* out);
private:
/**
* Adds the 'queryPlanner' explain section to the BSON object being built
* by 'out'.
*
* This is a helper for generating explain BSON. It is used by explainStages(...).
*
* - 'exec' is the stage tree for the operation being explained.
* - 'collection' is the collection used in the operation. The caller should hold an IS lock on
* the collection which the query is for, even if 'collection' is nullptr.
* - 'out' is a builder for the explain output.
*/
static void generatePlannerInfo(PlanExecutor* exec,
const Collection* collection,
BSONObjBuilder* out);
/**
* Private helper that does the heavy-lifting for the public statsToBSON(...) functions
* declared above.
*
* Not used except as a helper to the public statsToBSON(...) functions.
*/
static void statsToBSON(const PlanStageStats& stats,
ExplainOptions::Verbosity verbosity,
BSONObjBuilder* bob,
BSONObjBuilder* topLevelBob);
/**
* Adds the "executionStats" field to out. Assumes PlanExecutor::executePlan() has been called
* and that verbosity >= kExecStats.
*
* If verbosity >= kExecAllPlans, it will include the "allPlansExecution" array.
*
* - 'execPlanStatus' is the value returned after executing the query.
* - 'winningPlanTrialStats' may be nullptr.
**/
static void generateExecutionInfo(PlanExecutor* exec,
ExplainOptions::Verbosity verbosity,
Status executePlanStatus,
PlanStageStats* winningPlanTrialStats,
BSONObjBuilder* out);
/**
* Adds the 'serverInfo' explain section to the BSON object being build
* by 'out'.
*
* This is a helper for generating explain BSON. It is used by explainStages(...).
*/
static void generateServerInfo(BSONObjBuilder* out);
};
} // namespace
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