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/**
* 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"
namespace mongo::ce {
/**
* 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;
// 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;
};
/**
* 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:
ScalarHistogram();
ScalarHistogram(sbe::value::Array bounds, std::vector<Bucket> buckets);
std::string toString() const;
std::string plot() const;
const sbe::value::Array& getBounds() const;
const std::vector<Bucket>& getBuckets() const;
bool empty() const {
return _buckets.empty();
}
private:
// Bucket bounds representing the **highest** value in each bucket.
sbe::value::Array _bounds;
std::vector<Bucket> _buckets;
};
} // namespace mongo::ce
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