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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "queryterm.h"
#include <cstdint>
namespace search::fef {
class TermFieldMatchData;
class MatchData;
}
namespace search::features {
/**
* This class is used to calculate the minimal forward and reverse term distance
* between two terms matching in the same field using the position information for both terms.
*
* The terms 'a' and 'b' matching the field 'a b x a' will give the following result:
* - forwardDist = 1
* - forwardTermPos = 0
* - reverseDist = 2
* - reverseTermPos = 1
*
* Note that if we have a phrase 'a b' and term 'c' matching the field 'a b x c' we will get:
* - forwardDist = 2 (between b and c)
* - forwardTermPos = 0 (pos of first word)
**/
class TermDistanceCalculator {
public:
/**
* Represents an undefined value.
**/
static const uint32_t UNDEFINED_VALUE;
/**
* Contains the result from running the calculator.
**/
struct Result {
uint32_t forwardDist; // min distance between term X and term Y in the field
uint32_t forwardTermPos; // the position of term X for that distance
uint32_t reverseDist; // min distance between term Y and term X in the field
uint32_t reverseTermPos; // the position of term Y for that distance
/**
* Creates a new object with undefined values.
**/
Result() { reset(); }
/**
* Creates a new object with the given values.
**/
Result(uint32_t fd, uint32_t ftp, uint32_t rd, uint32_t rtp) :
forwardDist(fd), forwardTermPos(ftp), reverseDist(rd), reverseTermPos(rtp) {}
/**
* Sets all variables to the undefined value.
**/
void reset() {
forwardDist = UNDEFINED_VALUE;
forwardTermPos = UNDEFINED_VALUE;
reverseDist = UNDEFINED_VALUE;
reverseTermPos = UNDEFINED_VALUE;
}
};
private:
static void findBest(const fef::TermFieldMatchData *tmdX,
const fef::TermFieldMatchData *tmdY,
uint32_t numTermsX,
uint32_t & bestDist,
uint32_t & bestPos);
public:
/**
* Calculates the min forward and reverse distances based on the given
* match data and field id. The calculated values are stored in the given result object.
* NB: Both query terms must have attached term fields with valid term field handles.
**/
static void run(const QueryTerm &termX, const QueryTerm &termY,
const fef::MatchData & match, uint32_t docId, Result & r);
};
}
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