1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
/**
* Copyright (C) 2013 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 <list>
#include <memory>
#include <vector>
#include "mongo/base/owned_pointer_vector.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/plan_stats.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/query/query_solution.h"
namespace mongo {
struct CandidatePlan;
struct PlanRankingDecision;
/**
* Ranks 2 or more plans.
*/
class PlanRanker {
public:
/**
* Returns index in 'candidates' of which plan is best.
* Populates 'why' with information relevant to how each plan fared in the ranking process.
* Caller owns pointers in 'why'.
* 'candidateOrder' holds indices into candidates ordered by score (winner in first element).
*/
static size_t pickBestPlan(const std::vector<CandidatePlan>& candidates,
PlanRankingDecision* why);
/**
* Assign the stats tree a 'goodness' score. The higher the score, the better
* the plan. The exact value isn't meaningful except for imposing a ranking.
*/
static double scoreTree(const PlanStageStats* stats);
};
/**
* A container holding one to-be-ranked plan and its associated/relevant data.
* Does not own any of its pointers.
*/
struct CandidatePlan {
CandidatePlan(QuerySolution* s, PlanStage* r, WorkingSet* w)
: solution(s), root(r), ws(w), failed(false) {}
#if defined(_MSC_VER) && _MSC_VER < 1900 // MVSC++ <= 2013 can't generate default move operations
CandidatePlan(CandidatePlan&& other)
: solution(std::move(other.solution)),
root(std::move(other.root)),
ws(std::move(other.ws)),
results(std::move(other.results)),
failed(std::move(other.failed)) {}
CandidatePlan& operator=(CandidatePlan&& other) {
solution = std::move(other.solution);
root = std::move(other.root);
ws = std::move(other.ws);
results = std::move(other.results);
failed = std::move(other.failed);
return *this;
}
#endif
std::unique_ptr<QuerySolution> solution;
PlanStage* root; // Not owned here.
WorkingSet* ws; // Not owned here.
// Any results produced during the plan's execution prior to ranking are retained here.
std::list<WorkingSetID> results;
bool failed;
};
/**
* Information about why a plan was picked to be the best. Data here is placed into the cache
* and used to compare expected performance with actual.
*/
struct PlanRankingDecision {
PlanRankingDecision() {}
/**
* Make a deep copy.
*/
PlanRankingDecision* clone() const {
PlanRankingDecision* decision = new PlanRankingDecision();
for (size_t i = 0; i < stats.size(); ++i) {
PlanStageStats* s = stats.vector()[i];
invariant(s);
decision->stats.mutableVector().push_back(s->clone());
}
decision->scores = scores;
decision->candidateOrder = candidateOrder;
return decision;
}
// Stats of all plans sorted in descending order by score.
// Owned by us.
OwnedPointerVector<PlanStageStats> stats;
// The "goodness" score corresponding to 'stats'.
// Sorted in descending order.
std::vector<double> scores;
// Ordering of original plans in descending of score.
// Filled in by PlanRanker::pickBestPlan(candidates, ...)
// so that candidates[candidateOrder[0]] refers to the best plan
// with corresponding cores[0] and stats[0]. Runner-up would be
// candidates[candidateOrder[1]] followed by
// candidates[candidateOrder[2]], ...
std::vector<size_t> candidateOrder;
};
} // namespace mongo
|
