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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/query/explain_options.h"
#include "mongo/db/query/plan_cache.h"
#include "mongo/db/query/plan_executor.h"
#include "mongo/db/query/plan_explainer.h"
#include "mongo/db/query/sbe_plan_cache.h"
namespace mongo {
class Collection;
class CollectionPtr;
class MultipleCollectionAccessor;
class OperationContext;
class PlanExecutorPipeline;
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'.
*
* The 'extraInfo' parameter specifies additional information to include into the output.
*
* The 'command' parameter represents the command object that is being explained.
*
* Does not take ownership of its arguments.
*
* During this call it may be required to execute the plan to collect statistics. If the
* PlanExecutor uses 'kLockExternally' lock policy, the caller should hold at least an IS lock
* on the collection the that the query runs on, even if 'collection' parameter 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 CollectionPtr& collection,
ExplainOptions::Verbosity verbosity,
BSONObj extraInfo,
const BSONObj& command,
BSONObjBuilder* out);
/**
* Similar to the above function, but takes in multiple collections instead to support
* aggregation that involves multiple collections (e.g. $lookup).
*/
static void explainStages(PlanExecutor* exec,
const MultipleCollectionAccessor& collections,
ExplainOptions::Verbosity verbosity,
BSONObj extraInfo,
const BSONObj& command,
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.
* - 'collections' are the relevant main and secondary collections (e.g. for $lookup). If the
* PlanExecutor uses 'kLockExternally' lock policy, the caller should hold the necessary db_raii
* object on the involved collections.
* - 'verbosity' is the verbosity level of the explain.
* - 'extraInfo' specifies additional information to include into the output.
* - '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.
* - 'command' represents the command object that is being explained.
* - 'out' is the builder for the explain output.
*/
static void explainStages(
PlanExecutor* exec,
const MultipleCollectionAccessor& collections,
ExplainOptions::Verbosity verbosity,
Status executePlanStatus,
boost::optional<PlanExplainer::PlanStatsDetails> winningPlanTrialStats,
BSONObj extraInfo,
const BSONObj& command,
BSONObjBuilder* out);
/**
* Gets explain BSON for the document sources contained by 'exec'. Use this function if you have
* a PlanExecutor for a pipeline and want to turn it into a human readable explain format.
*
* The explain information is generated with the level of detail specified by 'verbosity'.
*
* If 'verbosity' >= 'kExecStats' the 'executePipeline' flag is used to indicate whether the
* pipeline needs to be executed first, before the stats is collected. Otherwise, it is assumed
* that the plan was already executed until EOF and the stats are ready for collection.
*
* The 'command' parameter represents the command object that is being explained.
*/
static void explainPipeline(PlanExecutor* exec,
bool executePipeline,
ExplainOptions::Verbosity verbosity,
const BSONObj& command,
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 mongo::PlanCacheEntry& entry, BSONObjBuilder* out);
static void planCacheEntryToBSON(const mongo::sbe::PlanCacheEntry& entry, BSONObjBuilder* out);
};
} // namespace mongo
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