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
|
/**
* Copyright (C) 2022-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 <string>
#include <utility>
#include <vector>
#include "mongo/db/exec/sbe/values/value.h"
#include "mongo/db/query/stats/stats_gen.h"
namespace mongo::stats {
/**
* Statistics related to a single ScalarHistogram bucket. The boundary value is kept in a separate
* array, so that each bucket has a corresponding boundary value. The reason for this to manage the
* memory of values.
*/
struct Bucket {
Bucket(double equalFreq,
double rangeFreq,
double cumulativeFreq,
double ndv,
double cumulativeNDV);
std::string toString() const;
// Help function to dump the bucket content as needed by histogram creation in the unit tests.
std::string dump() const;
// Frequency of the bound value itself.
double _equalFreq;
// Frequency of other values.
double _rangeFreq;
// Sum of frequencies of preceding buckets to avoid recomputing. Includes both _equalFreq and
// _rangeFreq.
double _cumulativeFreq;
// Number of distinct values in this bucket, excludes the bound.
double _ndv;
// Sum of distinct values in preceding buckets including this bucket.
double _cumulativeNDV;
// Serialize to BSON for storage in stats collection.
BSONObj serialize() const;
};
/**
* A ScalarHistogram over a set of values. The ScalarHistogram consists of two parallel vectors -
* one with the individual value statistics, and another one with the actual boundary values.
*/
class ScalarHistogram {
public:
/**
* Factory method for constructing an empty scalar histogram.
*/
static ScalarHistogram make();
/**
* Factory method for constructing a scalar histogram from a stats IDL StatsHistogram.
*/
static ScalarHistogram make(const StatsHistogram& histogram);
/**
* Factory method for constructing a scalar histogram from bounds & buckets.
*/
static ScalarHistogram make(sbe::value::Array bounds,
std::vector<Bucket> buckets,
bool doValidation = true);
// Print a human-readable representation of a histogram.
std::string toString() const;
std::string plot() const;
// Help function to dump the content of the histogram as needed by the manual histogram creation
// in the unit tests (without cummulative frequency and NDV).
std::string dump() const;
const sbe::value::Array& getBounds() const;
const std::vector<Bucket>& getBuckets() const;
// Return the total number of histogrammed values.
double getCardinality() const {
if (_buckets.empty()) {
return 0.0;
}
return _buckets.back()._cumulativeFreq;
}
bool empty() const {
return _buckets.empty();
}
// Serialize to BSON for storage in stats collection.
BSONObj serialize() const;
static constexpr size_t kMaxBuckets = 100;
private:
ScalarHistogram();
ScalarHistogram(sbe::value::Array bounds, std::vector<Bucket> buckets);
// Bucket bounds representing the **highest** value in each bucket.
const sbe::value::Array _bounds;
const std::vector<Bucket> _buckets;
};
} // namespace mongo::stats
|
