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/*----------------------------------------------------------------------------
*
* jaro.c
*
* Jaro Distance [1] is a similarity measure
*
* 1 m 1 m 1 m - t
* s = --- * ----- + --- * ----- + --- * -------
* 3 |a| 3 |b| 3 m
*
* where m is the number of matching characters [2], t is the number of
* transpositions [3], |a| is the length of string a and |b| is the length of
* string b.
*
* [2] two characters from a and b are considered matching iif they're not
* farther than floor(max(|a|, |b|) / 2) - 1.
*
* [3] number of transpositions is the number of matchings that are in a
* different sequence order divided by 2.
*
* Jaro-Winkler [4] Distance is a similarity measure
*
* It's an improvement over Jaro's original work. It gives more weight if the
* initial characters are the same. So,
*
* w = s + (l * p * (1 - s))
*
* where l is the length of common prefix up to 4 characters, p is a scaling
* factor (Winkler's suggestion is 0.1), and s is the Jaro Distance.
*
* For example:
*
* x: euler
* y: heuser
*
* 1 4 1 4 1 4 - 0 4 2 1
* s = --- * --- + --- * --- + --- * ------- = ---- + --- + --- = 0.822...
* 3 5 3 6 3 4 15 9 3
*
*
* w = 0.822 + (0 * 0.1 * (1 - 0.822)) = 0.822...
*
*
* [1] Jaro, M. A. (1989). "Advances in record linking methodology as applied
* to the 1985 census of Tampa Florida". Journal of the American Statistical
* Society 84 (406): 414–20.
*
* [4] Winkler, W. E. (2006). "Overview of Record Linkage and Current Research
* Directions". Research Report Series, RRS.
* http://www.census.gov/srd/papers/pdf/rrs2006-02.pdf.
*
*
* Copyright (c) 2008-2018, Euler Taveira de Oliveira
*
*----------------------------------------------------------------------------
*/
#include "similarity.h"
#include <math.h>
/* GUC variables */
double pgs_jaro_threshold = 0.7f;
bool pgs_jaro_is_normalized = true;
double pgs_jarowinkler_threshold = 0.7f;
bool pgs_jarowinkler_is_normalized = true;
static double _jaro(char *a, char *b)
{
int alen, blen;
int i, j, k;
int cd; /* common window distance */
int cc = 0; /* number of common characters */
int tr = 0; /* number of transpositions */
double res;
int *amatch; /* matchs in string a; match = 1; unmatch = 0 !! USED? !!*/
int *bmatch; /* matchs in string b; match = 1; unmatch = 0 */
int *posa; /* positions of matched characters in a */
int *posb; /* positions of matched characters in b */
alen = strlen(a);
blen = strlen(b);
elog(DEBUG1, "alen: %d; blen: %d", alen, blen);
if (alen > PGS_MAX_STR_LEN || blen > PGS_MAX_STR_LEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds the maximum length of %d bytes",
PGS_MAX_STR_LEN)));
/* if one string has zero length then return zero */
if (alen == 0 || blen == 0)
return 0.0;
/*
* allocate 2 vectors of integers. each position will be 0 or 1 depending
* on the character in that position is found between common window distance.
*/
amatch = palloc(sizeof(int) * alen);
bmatch = palloc(sizeof(int) * blen);
for (i = 0; i < alen; i++)
amatch[i] = 0;
for (j = 0; j < blen; j++)
bmatch[j] = 0;
/* common window distance is floor(max(alen, blen) / 2) - 1 */
cd = (int) floor((alen > blen ? alen : blen) / 2) - 1;
/* catch case when alen = blen = 1 */
if (cd < 0)
cd = 0;
elog(DEBUG1, "common window distance: %d", cd);
#ifdef PGS_IGNORE_CASE
elog(DEBUG2, "case-sensitive turns off");
for (i = 0; i < alen; i++)
a[i] = tolower(a[i]);
for (j = 0; j < blen; j++)
b[j] = tolower(b[j]);
#endif
for (i = 0; i < alen; i++)
{
/*
* calculate window test limits. limit inf to 0 and sup to blen
*/
int inf = max2(i - cd, 0);
int sup = i + cd + 1;
sup = min2(sup, blen);
/*
* no more common characters 'cause we don't have characters in b
* to test with characters in a
*/
if (inf >= sup)
break;
for (j = inf; j < sup; j++)
{
/*
* if found some match and it's not matched yet:
* (i) flag match characters in a and b
* (ii) increment cc
*/
if (bmatch[j] != 1 && a[i] == b[j])
{
amatch[i] = 1;
bmatch[j] = 1;
cc++;
break;
}
}
}
elog(DEBUG1, "common characters: %d", cc);
/* no common characters then return 0 */
if (cc == 0)
return 0.0;
/* allocate vector of positions */
posa = palloc(sizeof(int) * cc);
posb = palloc(sizeof(int) * cc);
k = 0;
for (i = 0; i < alen; i++)
{
if (amatch[i] == 1)
{
posa[k] = i;
k++;
}
}
k = 0;
for (j = 0; j < blen; j++)
{
if (bmatch[j] == 1)
{
posb[k] = j;
k++;
}
}
pfree(amatch);
pfree(bmatch);
/* counting half-transpositions */
for (i = 0; i < cc; i++)
if (a[posa[i]] != b[posb[i]])
tr++;
pfree(posa);
pfree(posb);
elog(DEBUG1, "half transpositions: %d", tr);
/* real number of transpositions */
tr /= 2;
elog(DEBUG1, "real transpositions: %d", tr);
res = PGS_JARO_W1 * cc / alen + PGS_JARO_W2 * cc / blen + PGS_JARO_WT * (cc - tr) / cc;
elog(DEBUG1, "jaro(%s, %s) = %f * %d / %d + %f * %d / %d + %f * (%d - %d) / %d = %f",
a, b, PGS_JARO_W1, cc, alen, PGS_JARO_W2, cc, blen, PGS_JARO_WT, cc, tr, cc, res);
return res;
}
PG_FUNCTION_INFO_V1(jaro);
Datum
jaro(PG_FUNCTION_ARGS)
{
char *a, *b;
float8 res;
a = DatumGetPointer(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
b = DatumGetPointer(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(1))));
res = _jaro(a, b);
elog(DEBUG1, "is normalized: %d", pgs_jaro_is_normalized);
elog(DEBUG1, "jaro(%s, %s) = %f", a, b, res);
/* normalized and unnormalized version are the same */
PG_RETURN_FLOAT8(res);
}
PG_FUNCTION_INFO_V1(jaro_op);
Datum jaro_op(PG_FUNCTION_ARGS)
{
float8 res;
/*
* store *_is_normalized value temporarily 'cause
* threshold (we're comparing against) is normalized
*/
bool tmp = pgs_jaro_is_normalized;
pgs_jaro_is_normalized = true;
res = DatumGetFloat8(DirectFunctionCall2(
jaro,
PG_GETARG_DATUM(0),
PG_GETARG_DATUM(1)));
/* we're done; back to the previous value */
pgs_jaro_is_normalized = tmp;
PG_RETURN_BOOL(res >= pgs_jaro_threshold);
}
PG_FUNCTION_INFO_V1(jarowinkler);
Datum
jarowinkler(PG_FUNCTION_ARGS)
{
char *a, *b;
float8 resj, res;
int i;
int plen = 0;
a = DatumGetPointer(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
b = DatumGetPointer(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(1))));
resj = _jaro(a, b);
res = resj;
elog(DEBUG1, "jaro(%s, %s) = %f", a, b, resj);
if (resj > PGS_JARO_BOOST_THRESHOLD)
{
for (i = 0; i < strlen(a) && i < strlen(b) && i < PGS_JARO_PREFIX_SIZE; i++)
{
if (a[i] == b[i])
plen++;
else
break;
}
elog(DEBUG1, "prefix length: %d", plen);
res += PGS_JARO_SCALING_FACTOR * plen * (1.0 - resj);
}
elog(DEBUG1, "is normalized: %d", pgs_jarowinkler_is_normalized);
elog(DEBUG1, "jarowinkler(%s, %s) = %f + %d * %f * (1.0 - %f) = %f",
a, b, resj, plen, PGS_JARO_SCALING_FACTOR, resj, res);
/* normalized and unnormalized version are the same */
PG_RETURN_FLOAT8(res);
}
PG_FUNCTION_INFO_V1(jarowinkler_op);
Datum jarowinkler_op(PG_FUNCTION_ARGS)
{
float8 res;
/*
* store *_is_normalized value temporarily 'cause
* threshold (we're comparing against) is normalized
*/
bool tmp = pgs_jarowinkler_is_normalized;
pgs_jarowinkler_is_normalized = true;
res = DatumGetFloat8(DirectFunctionCall2(
jarowinkler,
PG_GETARG_DATUM(0),
PG_GETARG_DATUM(1)));
/* we're done; back to the previous value */
pgs_jarowinkler_is_normalized = tmp;
PG_RETURN_BOOL(res >= pgs_jarowinkler_threshold);
}
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