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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/db/query/all_indices_required_checker.h"
#include "mongo/db/query/query_planner_params.h"
#include "mongo/db/query/sbe_plan_ranker.h"
#include "mongo/db/query/sbe_runtime_planner.h"
namespace mongo::sbe {
/**
* Runs a trial period in order to evaluate the cost of a cached plan. If the cost is unexpectedly
* high, the plan cache entry is deactivated and we use multi-planning to select an entirely new
* winning plan. This process is called "replanning".
*
* TODO: refresh the list of indexes in 'queryParams' during replanning.
*/
class CachedSolutionPlanner final : public BaseRuntimePlanner {
public:
CachedSolutionPlanner(OperationContext* opCtx,
const CollectionPtr& collection,
const CanonicalQuery& cq,
const QueryPlannerParams& queryParams,
size_t decisionReads,
PlanYieldPolicySBE* yieldPolicy,
std::unique_ptr<plan_cache_debug_info::DebugInfoSBE> debugInfo)
: BaseRuntimePlanner{opCtx, collection, cq, yieldPolicy},
_queryParams{queryParams},
_decisionReads{decisionReads},
_debugInfo{std::move(debugInfo)} {}
CandidatePlans plan(
std::vector<std::unique_ptr<QuerySolution>> solutions,
std::vector<std::pair<std::unique_ptr<PlanStage>, stage_builder::PlanStageData>> roots)
final;
private:
/**
* Executes the "trial" portion of a single plan until it
* - reaches EOF,
* - reaches the 'maxNumResults' limit,
* - early exits via the TrialRunTracker, or
* - returns a failure Status.
*
* All documents returned by the plan are enqueued into the 'CandidatePlan->results' queue.
*
* When the trial period ends, this function checks the stats to determine if the number of
* reads during the trial meets the criteria for replanning, in which case it sets the
* 'needsReplanning' flag of the resulting CandidatePlan to true.
*
* The execution plan for the resulting CandidatePlan remains open, but if the 'exitedEarly'
* flag is set, the plan is in an invalid state and must be closed and reopened before it can be
* executed.
*/
plan_ranker::CandidatePlan collectExecutionStatsForCachedPlan(
std::unique_ptr<QuerySolution> solution,
std::unique_ptr<PlanStage> root,
stage_builder::PlanStageData data,
size_t maxTrialPeriodNumReads);
/**
* Uses the QueryPlanner and the MultiPlanner to re-generate candidate plans for this
* query and select a new winner.
*
* Falls back to a new plan if the performance was worse than anticipated during the trial
* period.
*
* The plan cache is modified only if 'shouldCache' is true. The 'reason' string is used to
* indicate the reason for replanning, which can be included, for example, into plan stats
* summary.
*/
CandidatePlans replan(bool shouldCache, std::string reason) const;
// Query parameters used to create a query solution when the plan was first created. Used during
// replanning.
const QueryPlannerParams _queryParams;
// The number of physical reads taken to decide on a winning plan when the plan was first
// cached.
const size_t _decisionReads;
// Stores plan cache entry information used as debug information or for "explain" purpose.
std::unique_ptr<plan_cache_debug_info::DebugInfoSBE> _debugInfo;
};
} // namespace mongo::sbe
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