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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/catalog/collection.h"
#include "mongo/db/exec/sbe/stages/stages.h"
#include "mongo/db/query/all_indices_required_checker.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/multiple_collection_accessor.h"
#include "mongo/db/query/plan_yield_policy_sbe.h"
#include "mongo/db/query/query_planner_params.h"
#include "mongo/db/query/query_solution.h"
#include "mongo/db/query/sbe_plan_ranker.h"
namespace mongo::sbe {
/**
* This struct holds a vector with all candidate plans evaluated by this RuntimePlanner, and an
* index pointing to the winning plan within this vector.
*/
struct CandidatePlans {
auto& winner() {
invariant(winnerIdx < plans.size());
return plans[winnerIdx];
}
std::vector<plan_ranker::CandidatePlan> plans;
size_t winnerIdx;
};
/**
* An interface to be implemented by all classes which can evaluate the cost of a PlanStage tree in
* order to pick the the best plan amongst those specified in 'roots' vector. Evaluation is done in
* runtime by collecting execution stats for each of the plans, and the best candidate plan is
* chosen according to certain criteria.
*/
class RuntimePlanner {
public:
virtual ~RuntimePlanner() = default;
virtual CandidatePlans plan(
std::vector<std::unique_ptr<QuerySolution>> solutions,
std::vector<std::pair<std::unique_ptr<PlanStage>, stage_builder::PlanStageData>> roots) = 0;
};
/**
* A base class for runtime planner which provides a method to perform a trial run for the candidate
* plan by executing each plan in a round-robin fashion and collecting execution stats. Each
* specific implementation can use the collected stats to select the best plan amongst the
* candidates.
*/
class BaseRuntimePlanner : public RuntimePlanner {
public:
BaseRuntimePlanner(OperationContext* opCtx,
const MultipleCollectionAccessor& collections,
const CanonicalQuery& cq,
const QueryPlannerParams& queryParams,
PlanYieldPolicySBE* yieldPolicy)
: _opCtx(opCtx),
_collections(collections),
_cq(cq),
_queryParams(queryParams),
_yieldPolicy(yieldPolicy),
_indexExistenceChecker(collections) {
invariant(_opCtx);
}
protected:
/**
* Fetches a next document from the given plan stage tree and the loaded document is placed into
* the candidate's plan result queue.
*
* Returns true if a document was fetched, and false if the plan stage tree reached EOF, an
* exception was thrown or the plan stage tree returned maxNumResults documents.
*
* If the plan stage throws a 'QueryExceededMemoryLimitNoDiskUseAllowed', it will be caught and
* the 'candidate->status' will be set. This failure is considered recoverable, as another
* candidate plan may require less memory, or may not contain a stage requiring spilling to disk
* at all.
*/
static bool fetchNextDocument(plan_ranker::CandidatePlan* candidate, size_t maxNumResults);
/**
* Prepares the given plan stage tree for execution, attaches it to the operation context and
* returns two slot accessors for the result and recordId slots. The caller should pass true
* for 'preparingFromCache' if the SBE plan being prepared is being recovered from the SBE plan
* cache.
*/
std::pair<sbe::value::SlotAccessor*, sbe::value::SlotAccessor*> prepareExecutionPlan(
PlanStage* root, stage_builder::PlanStageData* data, bool preparingFromCache) const;
/**
* Wraps prepareExecutionPlan(), checks index validity, and caches outputAccessors.
*/
void prepareCandidate(plan_ranker::CandidatePlan* candidate, bool preparingFromCache);
void executeCachedCandidateTrial(plan_ranker::CandidatePlan* candidate, size_t maxNumResults);
OperationContext* const _opCtx;
const MultipleCollectionAccessor& _collections;
const CanonicalQuery& _cq;
const QueryPlannerParams _queryParams;
PlanYieldPolicySBE* const _yieldPolicy;
const AllIndicesRequiredChecker _indexExistenceChecker;
std::vector<plan_ranker::CandidatePlan> _candidates;
};
} // namespace mongo::sbe
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