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postgresql/contrib/fuzzystrmatch/fuzzystrmatch.c
Bruce Momjian 511db38ace Update copyright for 2009.
2009-01-01 17:24:05 +00:00

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/*
* fuzzystrmatch.c
*
* Functions for "fuzzy" comparison of strings
*
* Joe Conway <mail@joeconway.com>
*
* $PostgreSQL: pgsql/contrib/fuzzystrmatch/fuzzystrmatch.c,v 1.28 2009/01/01 17:23:32 momjian Exp $
* Copyright (c) 2001-2009, PostgreSQL Global Development Group
* ALL RIGHTS RESERVED;
*
* levenshtein()
* -------------
* Written based on a description of the algorithm by Michael Gilleland
* found at http://www.merriampark.com/ld.htm
* Also looked at levenshtein.c in the PHP 4.0.6 distribution for
* inspiration.
* Configurable penalty costs extension is introduced by Volkan
* YAZICI <volkan.yazici@gmail.com>.
*
* metaphone()
* -----------
* Modified for PostgreSQL by Joe Conway.
* Based on CPAN's "Text-Metaphone-1.96" by Michael G Schwern <schwern@pobox.com>
* Code slightly modified for use as PostgreSQL function (palloc, elog, etc).
* Metaphone was originally created by Lawrence Philips and presented in article
* in "Computer Language" December 1990 issue.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose, without fee, and without a written agreement
* is hereby granted, provided that the above copyright notice and this
* paragraph and the following two paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
*/
#include "postgres.h"
#include <ctype.h>
#include "fmgr.h"
#include "utils/builtins.h"
PG_MODULE_MAGIC;
/*
* External declarations for exported functions
*/
extern Datum levenshtein_with_costs(PG_FUNCTION_ARGS);
extern Datum levenshtein(PG_FUNCTION_ARGS);
extern Datum metaphone(PG_FUNCTION_ARGS);
extern Datum soundex(PG_FUNCTION_ARGS);
extern Datum difference(PG_FUNCTION_ARGS);
/*
* Soundex
*/
static void _soundex(const char *instr, char *outstr);
#define SOUNDEX_LEN 4
/* ABCDEFGHIJKLMNOPQRSTUVWXYZ */
static const char *soundex_table = "01230120022455012623010202";
#define soundex_code(letter) soundex_table[toupper((unsigned char) (letter)) - 'A']
/*
* Levenshtein
*/
#define MAX_LEVENSHTEIN_STRLEN 255
static int levenshtein_internal(const char *s, const char *t,
int ins_c, int del_c, int sub_c);
/*
* Metaphone
*/
#define MAX_METAPHONE_STRLEN 255
/*
* Original code by Michael G Schwern starts here.
* Code slightly modified for use as PostgreSQL function.
*/
/**************************************************************************
metaphone -- Breaks english phrases down into their phonemes.
Input
word -- An english word to be phonized
max_phonemes -- How many phonemes to calculate. If 0, then it
will phonize the entire phrase.
phoned_word -- The final phonized word. (We'll allocate the
memory.)
Output
error -- A simple error flag, returns TRUE or FALSE
NOTES: ALL non-alpha characters are ignored, this includes whitespace,
although non-alpha characters will break up phonemes.
****************************************************************************/
/**************************************************************************
my constants -- constants I like
Probably redundant.
***************************************************************************/
#define META_ERROR FALSE
#define META_SUCCESS TRUE
#define META_FAILURE FALSE
/* I add modifications to the traditional metaphone algorithm that you
might find in books. Define this if you want metaphone to behave
traditionally */
#undef USE_TRADITIONAL_METAPHONE
/* Special encodings */
#define SH 'X'
#define TH '0'
static char Lookahead(char *word, int how_far);
static int _metaphone(char *word, int max_phonemes, char **phoned_word);
/* Metachar.h ... little bits about characters for metaphone */
/*-- Character encoding array & accessing macros --*/
/* Stolen directly out of the book... */
char _codes[26] = {
1, 16, 4, 16, 9, 2, 4, 16, 9, 2, 0, 2, 2, 2, 1, 4, 0, 2, 4, 4, 1, 0, 0, 0, 8, 0
/* a b c d e f g h i j k l m n o p q r s t u v w x y z */
};
#define ENCODE(c) (isalpha((unsigned char) (c)) ? _codes[((toupper((unsigned char) (c))) - 'A')] : 0)
#define isvowel(c) (ENCODE(c) & 1) /* AEIOU */
/* These letters are passed through unchanged */
#define NOCHANGE(c) (ENCODE(c) & 2) /* FJMNR */
/* These form dipthongs when preceding H */
#define AFFECTH(c) (ENCODE(c) & 4) /* CGPST */
/* These make C and G soft */
#define MAKESOFT(c) (ENCODE(c) & 8) /* EIY */
/* These prevent GH from becoming F */
#define NOGHTOF(c) (ENCODE(c) & 16) /* BDH */
/*
* levenshtein_internal - Calculates Levenshtein distance metric
* between supplied strings. Generally
* (1, 1, 1) penalty costs suffices common
* cases, but your mileage may vary.
*/
static int
levenshtein_internal(const char *s, const char *t,
int ins_c, int del_c, int sub_c)
{
int m, n;
int *prev;
int *curr;
int i, j;
const char *x;
const char *y;
m = strlen(s);
n = strlen(t);
/*
* If either m or n is 0, the answer is the other value. This makes
* sense since it would take that many insertions to build a matching
* string
*/
if (!m)
return n;
if (!n)
return m;
/*
* For security concerns, restrict excessive CPU+RAM usage. (This
* implementation uses O(m) memory and has O(mn) complexity.)
*/
if (m > MAX_LEVENSHTEIN_STRLEN ||
n > MAX_LEVENSHTEIN_STRLEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds the maximum length of %d bytes",
MAX_LEVENSHTEIN_STRLEN)));
/* One more cell for initialization column and row. */
++m;
++n;
/*
* Instead of building an (m+1)x(n+1) array, we'll use two
* different arrays of size m+1 for storing accumulated values.
* At each step one represents the "previous" row and one is the
* "current" row of the notional large array.
*/
prev = (int *) palloc(2 * m * sizeof(int));
curr = prev + m;
/* Initialize the "previous" row to 0..cols */
for (i = 0; i < m; i++)
prev[i] = i;
/* Loop through rows of the notional array */
for (y = t, j = 1; j < n; y++, j++)
{
int *temp;
/*
* First cell must increment sequentially, as we're on the
* j'th row of the (m+1)x(n+1) array.
*/
curr[0] = j;
for (x = s, i = 1; i < m; x++, i++)
{
int ins;
int del;
int sub;
/* Calculate costs for probable operations. */
ins = prev[i] + ins_c; /* Insertion */
del = curr[i-1] + del_c; /* Deletion */
sub = prev[i-1] + ((*x == *y) ? 0 : sub_c); /* Substitution */
/* Take the one with minimum cost. */
curr[i] = Min(ins, del);
curr[i] = Min(curr[i], sub);
}
/* Swap current row with previous row. */
temp = curr;
curr = prev;
prev = temp;
}
/*
* Because the final value was swapped from the previous row to
* the current row, that's where we'll find it.
*/
return prev[m-1];
}
PG_FUNCTION_INFO_V1(levenshtein_with_costs);
Datum
levenshtein_with_costs(PG_FUNCTION_ARGS)
{
char *src = TextDatumGetCString(PG_GETARG_DATUM(0));
char *dst = TextDatumGetCString(PG_GETARG_DATUM(1));
int ins_c = PG_GETARG_INT32(2);
int del_c = PG_GETARG_INT32(3);
int sub_c = PG_GETARG_INT32(4);
PG_RETURN_INT32(levenshtein_internal(src, dst, ins_c, del_c, sub_c));
}
PG_FUNCTION_INFO_V1(levenshtein);
Datum
levenshtein(PG_FUNCTION_ARGS)
{
char *src = TextDatumGetCString(PG_GETARG_DATUM(0));
char *dst = TextDatumGetCString(PG_GETARG_DATUM(1));
PG_RETURN_INT32(levenshtein_internal(src, dst, 1, 1, 1));
}
/*
* Calculates the metaphone of an input string.
* Returns number of characters requested
* (suggested value is 4)
*/
PG_FUNCTION_INFO_V1(metaphone);
Datum
metaphone(PG_FUNCTION_ARGS)
{
char *str_i = TextDatumGetCString(PG_GETARG_DATUM(0));
size_t str_i_len = strlen(str_i);
int reqlen;
char *metaph;
int retval;
/* return an empty string if we receive one */
if (!(str_i_len > 0))
PG_RETURN_TEXT_P(cstring_to_text(""));
if (str_i_len > MAX_METAPHONE_STRLEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds the maximum length of %d bytes",
MAX_METAPHONE_STRLEN)));
if (!(str_i_len > 0))
ereport(ERROR,
(errcode(ERRCODE_ZERO_LENGTH_CHARACTER_STRING),
errmsg("argument is empty string")));
reqlen = PG_GETARG_INT32(1);
if (reqlen > MAX_METAPHONE_STRLEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("output exceeds the maximum length of %d bytes",
MAX_METAPHONE_STRLEN)));
if (!(reqlen > 0))
ereport(ERROR,
(errcode(ERRCODE_ZERO_LENGTH_CHARACTER_STRING),
errmsg("output cannot be empty string")));
retval = _metaphone(str_i, reqlen, &metaph);
if (retval == META_SUCCESS)
PG_RETURN_TEXT_P(cstring_to_text(metaph));
else
{
/* internal error */
elog(ERROR, "metaphone: failure");
/* keep the compiler quiet */
PG_RETURN_NULL();
}
}
/*
* Original code by Michael G Schwern starts here.
* Code slightly modified for use as PostgreSQL
* function (palloc, etc).
*/
/* I suppose I could have been using a character pointer instead of
* accessing the array directly... */
/* Look at the next letter in the word */
#define Next_Letter (toupper((unsigned char) word[w_idx+1]))
/* Look at the current letter in the word */
#define Curr_Letter (toupper((unsigned char) word[w_idx]))
/* Go N letters back. */
#define Look_Back_Letter(n) \
(w_idx >= (n) ? toupper((unsigned char) word[w_idx-(n)]) : '\0')
/* Previous letter. I dunno, should this return null on failure? */
#define Prev_Letter (Look_Back_Letter(1))
/* Look two letters down. It makes sure you don't walk off the string. */
#define After_Next_Letter \
(Next_Letter != '\0' ? toupper((unsigned char) word[w_idx+2]) : '\0')
#define Look_Ahead_Letter(n) toupper((unsigned char) Lookahead(word+w_idx, n))
/* Allows us to safely look ahead an arbitrary # of letters */
/* I probably could have just used strlen... */
static char
Lookahead(char *word, int how_far)
{
char letter_ahead = '\0'; /* null by default */
int idx;
for (idx = 0; word[idx] != '\0' && idx < how_far; idx++);
/* Edge forward in the string... */
letter_ahead = word[idx]; /* idx will be either == to how_far or at the
* end of the string */
return letter_ahead;
}
/* phonize one letter */
#define Phonize(c) do {(*phoned_word)[p_idx++] = c;} while (0)
/* Slap a null character on the end of the phoned word */
#define End_Phoned_Word do {(*phoned_word)[p_idx] = '\0';} while (0)
/* How long is the phoned word? */
#define Phone_Len (p_idx)
/* Note is a letter is a 'break' in the word */
#define Isbreak(c) (!isalpha((unsigned char) (c)))
static int
_metaphone(char *word, /* IN */
int max_phonemes,
char **phoned_word) /* OUT */
{
int w_idx = 0; /* point in the phonization we're at. */
int p_idx = 0; /* end of the phoned phrase */
/*-- Parameter checks --*/
/*
* Shouldn't be necessary, but left these here anyway jec Aug 3, 2001
*/
/* Negative phoneme length is meaningless */
if (!(max_phonemes > 0))
/* internal error */
elog(ERROR, "metaphone: Requested output length must be > 0");
/* Empty/null string is meaningless */
if ((word == NULL) || !(strlen(word) > 0))
/* internal error */
elog(ERROR, "metaphone: Input string length must be > 0");
/*-- Allocate memory for our phoned_phrase --*/
if (max_phonemes == 0)
{ /* Assume largest possible */
*phoned_word = palloc(sizeof(char) * strlen(word) +1);
}
else
{
*phoned_word = palloc(sizeof(char) * max_phonemes + 1);
}
/*-- The first phoneme has to be processed specially. --*/
/* Find our first letter */
for (; !isalpha((unsigned char) (Curr_Letter)); w_idx++)
{
/* On the off chance we were given nothing but crap... */
if (Curr_Letter == '\0')
{
End_Phoned_Word;
return META_SUCCESS; /* For testing */
}
}
switch (Curr_Letter)
{
/* AE becomes E */
case 'A':
if (Next_Letter == 'E')
{
Phonize('E');
w_idx += 2;
}
/* Remember, preserve vowels at the beginning */
else
{
Phonize('A');
w_idx++;
}
break;
/* [GKP]N becomes N */
case 'G':
case 'K':
case 'P':
if (Next_Letter == 'N')
{
Phonize('N');
w_idx += 2;
}
break;
/*
* WH becomes H, WR becomes R W if followed by a vowel
*/
case 'W':
if (Next_Letter == 'H' ||
Next_Letter == 'R')
{
Phonize(Next_Letter);
w_idx += 2;
}
else if (isvowel(Next_Letter))
{
Phonize('W');
w_idx += 2;
}
/* else ignore */
break;
/* X becomes S */
case 'X':
Phonize('S');
w_idx++;
break;
/* Vowels are kept */
/*
* We did A already case 'A': case 'a':
*/
case 'E':
case 'I':
case 'O':
case 'U':
Phonize(Curr_Letter);
w_idx++;
break;
default:
/* do nothing */
break;
}
/* On to the metaphoning */
for (; Curr_Letter != '\0' &&
(max_phonemes == 0 || Phone_Len < max_phonemes);
w_idx++)
{
/*
* How many letters to skip because an earlier encoding handled
* multiple letters
*/
unsigned short int skip_letter = 0;
/*
* THOUGHT: It would be nice if, rather than having things like...
* well, SCI. For SCI you encode the S, then have to remember to skip
* the C. So the phonome SCI invades both S and C. It would be
* better, IMHO, to skip the C from the S part of the encoding. Hell,
* I'm trying it.
*/
/* Ignore non-alphas */
if (!isalpha((unsigned char) (Curr_Letter)))
continue;
/* Drop duplicates, except CC */
if (Curr_Letter == Prev_Letter &&
Curr_Letter != 'C')
continue;
switch (Curr_Letter)
{
/* B -> B unless in MB */
case 'B':
if (Prev_Letter != 'M')
Phonize('B');
break;
/*
* 'sh' if -CIA- or -CH, but not SCH, except SCHW. (SCHW is
* handled in S) S if -CI-, -CE- or -CY- dropped if -SCI-,
* SCE-, -SCY- (handed in S) else K
*/
case 'C':
if (MAKESOFT(Next_Letter))
{ /* C[IEY] */
if (After_Next_Letter == 'A' &&
Next_Letter == 'I')
{ /* CIA */
Phonize(SH);
}
/* SC[IEY] */
else if (Prev_Letter == 'S')
{
/* Dropped */
}
else
Phonize('S');
}
else if (Next_Letter == 'H')
{
#ifndef USE_TRADITIONAL_METAPHONE
if (After_Next_Letter == 'R' ||
Prev_Letter == 'S')
{ /* Christ, School */
Phonize('K');
}
else
Phonize(SH);
#else
Phonize(SH);
#endif
skip_letter++;
}
else
Phonize('K');
break;
/*
* J if in -DGE-, -DGI- or -DGY- else T
*/
case 'D':
if (Next_Letter == 'G' &&
MAKESOFT(After_Next_Letter))
{
Phonize('J');
skip_letter++;
}
else
Phonize('T');
break;
/*
* F if in -GH and not B--GH, D--GH, -H--GH, -H---GH else
* dropped if -GNED, -GN, else dropped if -DGE-, -DGI- or
* -DGY- (handled in D) else J if in -GE-, -GI, -GY and not GG
* else K
*/
case 'G':
if (Next_Letter == 'H')
{
if (!(NOGHTOF(Look_Back_Letter(3)) ||
Look_Back_Letter(4) == 'H'))
{
Phonize('F');
skip_letter++;
}
else
{
/* silent */
}
}
else if (Next_Letter == 'N')
{
if (Isbreak(After_Next_Letter) ||
(After_Next_Letter == 'E' &&
Look_Ahead_Letter(3) == 'D'))
{
/* dropped */
}
else
Phonize('K');
}
else if (MAKESOFT(Next_Letter) &&
Prev_Letter != 'G')
Phonize('J');
else
Phonize('K');
break;
/* H if before a vowel and not after C,G,P,S,T */
case 'H':
if (isvowel(Next_Letter) &&
!AFFECTH(Prev_Letter))
Phonize('H');
break;
/*
* dropped if after C else K
*/
case 'K':
if (Prev_Letter != 'C')
Phonize('K');
break;
/*
* F if before H else P
*/
case 'P':
if (Next_Letter == 'H')
Phonize('F');
else
Phonize('P');
break;
/*
* K
*/
case 'Q':
Phonize('K');
break;
/*
* 'sh' in -SH-, -SIO- or -SIA- or -SCHW- else S
*/
case 'S':
if (Next_Letter == 'I' &&
(After_Next_Letter == 'O' ||
After_Next_Letter == 'A'))
Phonize(SH);
else if (Next_Letter == 'H')
{
Phonize(SH);
skip_letter++;
}
#ifndef USE_TRADITIONAL_METAPHONE
else if (Next_Letter == 'C' &&
Look_Ahead_Letter(2) == 'H' &&
Look_Ahead_Letter(3) == 'W')
{
Phonize(SH);
skip_letter += 2;
}
#endif
else
Phonize('S');
break;
/*
* 'sh' in -TIA- or -TIO- else 'th' before H else T
*/
case 'T':
if (Next_Letter == 'I' &&
(After_Next_Letter == 'O' ||
After_Next_Letter == 'A'))
Phonize(SH);
else if (Next_Letter == 'H')
{
Phonize(TH);
skip_letter++;
}
else
Phonize('T');
break;
/* F */
case 'V':
Phonize('F');
break;
/* W before a vowel, else dropped */
case 'W':
if (isvowel(Next_Letter))
Phonize('W');
break;
/* KS */
case 'X':
Phonize('K');
if (max_phonemes == 0 || Phone_Len < max_phonemes)
Phonize('S');
break;
/* Y if followed by a vowel */
case 'Y':
if (isvowel(Next_Letter))
Phonize('Y');
break;
/* S */
case 'Z':
Phonize('S');
break;
/* No transformation */
case 'F':
case 'J':
case 'L':
case 'M':
case 'N':
case 'R':
Phonize(Curr_Letter);
break;
default:
/* nothing */
break;
} /* END SWITCH */
w_idx += skip_letter;
} /* END FOR */
End_Phoned_Word;
return (META_SUCCESS);
} /* END metaphone */
/*
* SQL function: soundex(text) returns text
*/
PG_FUNCTION_INFO_V1(soundex);
Datum
soundex(PG_FUNCTION_ARGS)
{
char outstr[SOUNDEX_LEN + 1];
char *arg;
arg = text_to_cstring(PG_GETARG_TEXT_P(0));
_soundex(arg, outstr);
PG_RETURN_TEXT_P(cstring_to_text(outstr));
}
static void
_soundex(const char *instr, char *outstr)
{
int count;
AssertArg(instr);
AssertArg(outstr);
outstr[SOUNDEX_LEN] = '\0';
/* Skip leading non-alphabetic characters */
while (!isalpha((unsigned char) instr[0]) && instr[0])
++instr;
/* No string left */
if (!instr[0])
{
outstr[0] = (char) 0;
return;
}
/* Take the first letter as is */
*outstr++ = (char) toupper((unsigned char) *instr++);
count = 1;
while (*instr && count < SOUNDEX_LEN)
{
if (isalpha((unsigned char) *instr) &&
soundex_code(*instr) != soundex_code(*(instr - 1)))
{
*outstr = soundex_code(instr[0]);
if (*outstr != '0')
{
++outstr;
++count;
}
}
++instr;
}
/* Fill with 0's */
while (count < SOUNDEX_LEN)
{
*outstr = '0';
++outstr;
++count;
}
}
PG_FUNCTION_INFO_V1(difference);
Datum
difference(PG_FUNCTION_ARGS)
{
char sndx1[SOUNDEX_LEN + 1],
sndx2[SOUNDEX_LEN + 1];
int i,
result;
_soundex(text_to_cstring(PG_GETARG_TEXT_P(0)), sndx1);
_soundex(text_to_cstring(PG_GETARG_TEXT_P(1)), sndx2);
result = 0;
for (i = 0; i < SOUNDEX_LEN; i++)
{
if (sndx1[i] == sndx2[i])
result++;
}
PG_RETURN_INT32(result);
}
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