mirror of https://gitee.com/bigwinds/arangodb
318 lines
11 KiB
C++
318 lines
11 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// @brief infrastructure for query optimizer
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///
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/// @file arangod/Aql/Optimizer.h
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///
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/// DISCLAIMER
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///
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/// Copyright 2010-2014 triagens GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is triAGENS GmbH, Cologne, Germany
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///
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/// @author Max Neunhoeffer
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/// @author Copyright 2014, triagens GmbH, Cologne, Germany
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGOD_AQL_OPTIMIZER_H
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#define ARANGOD_AQL_OPTIMIZER_H 1
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#include <Basics/Common.h>
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#include "Aql/ExecutionPlan.h"
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namespace triagens {
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namespace aql {
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// -----------------------------------------------------------------------------
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// --SECTION-- the optimizer class
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// -----------------------------------------------------------------------------
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class Optimizer {
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public:
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////////////////////////////////////////////////////////////////////////////////
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/// @brief the following struct keeps a list (deque) of ExecutionPlan*
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/// and has some automatic convenience functions.
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////////////////////////////////////////////////////////////////////////////////
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struct PlanList {
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std::deque<ExecutionPlan*> list;
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////////////////////////////////////////////////////////////////////////////////
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/// @brief constructor
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////////////////////////////////////////////////////////////////////////////////
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PlanList () {};
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////////////////////////////////////////////////////////////////////////////////
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/// @brief constructor with a plan
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////////////////////////////////////////////////////////////////////////////////
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PlanList (ExecutionPlan* p) {
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list.push_back(p);
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief destructor, deleting contents
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////////////////////////////////////////////////////////////////////////////////
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~PlanList () {
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for (auto p : list) {
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delete p;
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}
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief get number of plans contained
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////////////////////////////////////////////////////////////////////////////////
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size_t size () const {
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return list.size();
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief pop the first one
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////////////////////////////////////////////////////////////////////////////////
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ExecutionPlan* pop_front () {
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auto p = list.front();
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list.pop_front();
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return p;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief push_back
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////////////////////////////////////////////////////////////////////////////////
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void push_back (ExecutionPlan* p) {
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list.push_back(p);
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief steals all the plans in b and clears b at the same time
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////////////////////////////////////////////////////////////////////////////////
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void steal (PlanList& b) {
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list.swap(b.list);
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for (auto p : b.list) {
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delete p;
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}
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b.list.clear();
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief appends all the plans to the target and clears *this at the same time
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////////////////////////////////////////////////////////////////////////////////
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void appendTo (std::vector<ExecutionPlan*>& target) {
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while (list.size() > 0) {
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auto p = list.front();
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list.pop_front();
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try {
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target.push_back(p);
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}
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catch (...) {
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delete p;
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throw;
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}
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}
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}
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};
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////////////////////////////////////////////////////////////////////////////////
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/// @brief type of an optimizer rule function, the function gets an optimiser,
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/// an ExecutionPlan and has to append one or more plans to the resulting
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/// deque. This must not include the original plan. The rule has to set keep
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/// to indicate whether or not the original plan is kept in the resulting
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/// list. Note that the optimization is done in multiple passes
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////////////////////////////////////////////////////////////////////////////////
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typedef std::function<int(Optimizer* opt,
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ExecutionPlan* plan,
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PlanList& out,
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bool& keep)>
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RuleFunction;
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////////////////////////////////////////////////////////////////////////////////
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/// @brief type of an optimizer rule
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////////////////////////////////////////////////////////////////////////////////
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struct Rule {
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RuleFunction func;
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int rank;
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Rule (RuleFunction f, int r)
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: func(f), rank(r) {
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief operator< for two rules, used to stable_sort by pass
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////////////////////////////////////////////////////////////////////////////////
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bool operator< (Rule const& b) const {
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return rank > b.rank;
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}
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};
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////////////////////////////////////////////////////////////////////////////////
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/// @brief number of passes in optimization
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////////////////////////////////////////////////////////////////////////////////
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static int const numberOfPasses = 3;
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////////////////////////////////////////////////////////////////////////////////
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/// @brief maximal number of plans to produce:
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////////////////////////////////////////////////////////////////////////////////
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static int const maxNumberOfPlans = 1000;
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////////////////////////////////////////////////////////////////////////////////
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/// @brief constructor, this will initialize the rules database
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////////////////////////////////////////////////////////////////////////////////
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Optimizer (); // the .cpp file includes Aql/OptimizerRules.h
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// and add all methods there to the rules database
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////////////////////////////////////////////////////////////////////////////////
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/// @brief destructor
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////////////////////////////////////////////////////////////////////////////////
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~Optimizer () {
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for (auto p : _plans) {
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delete p;
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}
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_plans.clear();
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief do the optimization, this does the optimization, the resulting
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/// plans are all estimated, sorted by that estimate and can then be got
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/// by getPlans, until the next initialize is called. Note that the optimizer
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/// object takes ownership of the execution plan and will delete it
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/// automatically on destruction. It will also have ownership of all the
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/// newly created plans it recalls and will automatically delete them.
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/// If you need to extract the plans from the optimizer use stealBest or
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/// stealPlans.
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////////////////////////////////////////////////////////////////////////////////
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int createPlans (ExecutionPlan* p);
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////////////////////////////////////////////////////////////////////////////////
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/// @brief getBest, ownership of the plan remains with the optimizer
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////////////////////////////////////////////////////////////////////////////////
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ExecutionPlan* getBest () {
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if (_plans.empty()) {
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return nullptr;
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}
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return _plans[0];
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief getPlans, ownership of the plans remains with the optimizer
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////////////////////////////////////////////////////////////////////////////////
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std::vector<ExecutionPlan*>& getPlans () {
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return _plans;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief stealBest, ownership of the plan is handed over to the caller,
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/// all other plans are deleted
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////////////////////////////////////////////////////////////////////////////////
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ExecutionPlan* stealBest () {
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if (_plans.empty()) {
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return nullptr;
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}
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auto res = _plans[0];
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for (size_t i = 1; i < _plans.size(); i++) {
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delete _plans[i];
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}
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_plans.clear();
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std::cout << res->toJson(TRI_UNKNOWN_MEM_ZONE, false).toString() << "\n";
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return res;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief stealPlans, ownership of the plans is handed over to the caller,
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/// the optimizer will forget about them!
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////////////////////////////////////////////////////////////////////////////////
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std::vector<ExecutionPlan*> stealPlans () {
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std::vector<ExecutionPlan*> res;
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res.swap(_plans);
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return res;
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- private methods
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// -----------------------------------------------------------------------------
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private:
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////////////////////////////////////////////////////////////////////////////////
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/// @brief registerRule
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////////////////////////////////////////////////////////////////////////////////
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void registerRule (RuleFunction f, int pass) {
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_rules.emplace_back(f, pass);
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief estimatePlans
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////////////////////////////////////////////////////////////////////////////////
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void estimatePlans ();
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////////////////////////////////////////////////////////////////////////////////
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/// @brief sortPlans
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////////////////////////////////////////////////////////////////////////////////
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void sortPlans ();
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// -----------------------------------------------------------------------------
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// --SECTION-- private members
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// -----------------------------------------------------------------------------
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private:
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////////////////////////////////////////////////////////////////////////////////
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/// @brief the rules database
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////////////////////////////////////////////////////////////////////////////////
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std::vector<Rule> _rules;
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////////////////////////////////////////////////////////////////////////////////
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/// @brief the current set of plans to be optimised
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////////////////////////////////////////////////////////////////////////////////
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std::vector<ExecutionPlan*> _plans;
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};
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} // namespace aql
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} // namespace triagens
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#endif
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// Local Variables:
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// mode: outline-minor
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// outline-regexp: "^\\(/// @brief\\|/// {@inheritDoc}\\|/// @addtogroup\\|// --SECTION--\\|/// @\\}\\)"
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// End:
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