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postgresql/contrib/fuzzystrmatch/fuzzystrmatch.c
Joe Conway 13629df5a1 Add double metaphone code from Andrew Dunstan. Also change metaphone so that 
an empty input string causes an empty output string to be returned, instead of
throwing an ERROR -- per complaint from Aaron Hillegass, and consistent with
double metaphone. Fix examples in README.soundex pointed out by James Robinson.
2004-07-01 03:25:48 +00:00

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/*
* fuzzystrmatch.c
*
* Functions for "fuzzy" comparison of strings
*
* Joe Conway <mail@joeconway.com>
*
* Copyright (c) 2001-2003, 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.
*
* 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 "fuzzystrmatch.h"
/*
* Calculates Levenshtein Distance between two strings.
* Uses simplest and fastest cost model only, i.e. assumes a cost of 1 for
* each deletion, substitution, or insertion.
*/
PG_FUNCTION_INFO_V1(levenshtein);
Datum
levenshtein(PG_FUNCTION_ARGS)
{
char *str_s;
char *str_s0;
char *str_t;
int cols = 0;
int rows = 0;
int *u_cells;
int *l_cells;
int *tmp;
int i;
int j;
/*
* Fetch the arguments. str_s is referred to as the "source" cols =
* length of source + 1 to allow for the initialization column str_t
* is referred to as the "target", rows = length of target + 1 rows =
* length of target + 1 to allow for the initialization row
*/
str_s = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
str_t = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(1))));
cols = strlen(str_s) + 1;
rows = strlen(str_t) + 1;
/*
* Restrict the length of the strings being compared to something
* reasonable because we will have to perform rows * cols
* calculations. If longer strings need to be compared, increase
* MAX_LEVENSHTEIN_STRLEN to suit (but within your tolerance for speed
* and memory usage).
*/
if ((cols > MAX_LEVENSHTEIN_STRLEN + 1) || (rows > MAX_LEVENSHTEIN_STRLEN + 1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds max length: %d",
MAX_LEVENSHTEIN_STRLEN)));
/*
* If either rows or cols is 0, the answer is the other value. This
* makes sense since it would take that many insertions the build a
* matching string
*/
if (cols == 0)
PG_RETURN_INT32(rows);
if (rows == 0)
PG_RETURN_INT32(cols);
/*
* Allocate two vectors of integers. One will be used for the "upper"
* row, the other for the "lower" row. Initialize the "upper" row to
* 0..cols
*/
u_cells = palloc(sizeof(int) * cols);
for (i = 0; i < cols; i++)
u_cells[i] = i;
l_cells = palloc(sizeof(int) * cols);
/*
* Use str_s0 to "rewind" the pointer to str_s in the nested for loop
* below
*/
str_s0 = str_s;
/*
* Loop throught the rows, starting at row 1. Row 0 is used for the
* initial "upper" row.
*/
for (j = 1; j < rows; j++)
{
/*
* We'll always start with col 1, and initialize lower row col 0
* to j
*/
l_cells[0] = j;
for (i = 1; i < cols; i++)
{
int c = 0;
int c1 = 0;
int c2 = 0;
int c3 = 0;
/*
* The "cost" value is 0 if the character at the current col
* position in the source string, matches the character at the
* current row position in the target string; cost is 1
* otherwise.
*/
c = ((CHAREQ(str_s, str_t)) ? 0 : 1);
/*
* c1 is upper right cell plus 1
*/
c1 = u_cells[i] + 1;
/*
* c2 is lower left cell plus 1
*/
c2 = l_cells[i - 1] + 1;
/*
* c3 is cell diagonally above to the left plus "cost"
*/
c3 = u_cells[i - 1] + c;
/*
* The lower right cell is set to the minimum of c1, c2, c3
*/
l_cells[i] = (c1 < c2 ? c1 : c2) < c3 ? (c1 < c2 ? c1 : c2) : c3;
/*
* Increment the pointer to str_s
*/
NextChar(str_s);
}
/*
* Lower row now becomes the upper row, and the upper row gets
* reused as the new lower row.
*/
tmp = u_cells;
u_cells = l_cells;
l_cells = tmp;
/*
* Increment the pointer to str_t
*/
NextChar(str_t);
/*
* Rewind the pointer to str_s
*/
str_s = str_s0;
}
/*
* Because the final value (at position row, col) was swapped from the
* lower row to the upper row, that's where we'll find it.
*/
PG_RETURN_INT32(u_cells[cols - 1]);
}
/*
* Calculates the metaphone of an input string.
* Returns number of characters requested
* (suggested value is 4)
*/
#define GET_TEXT(cstrp) DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(cstrp)))
PG_FUNCTION_INFO_V1(metaphone);
Datum
metaphone(PG_FUNCTION_ARGS)
{
int reqlen;
char *str_i;
size_t str_i_len;
char *metaph;
text *result_text;
int retval;
str_i = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
str_i_len = strlen(str_i);
/* return an empty string if we receive one */
if (!(str_i_len > 0))
PG_RETURN_TEXT_P(GET_TEXT(""));
if (str_i_len > MAX_METAPHONE_STRLEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds max length: %d",
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 length exceeds max length: %d",
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)
{
result_text = DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(metaph)));
PG_RETURN_TEXT_P(result_text);
}
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). Original includes
* are rolled into fuzzystrmatch.h
*------------------------------------------------------------------*/
/* 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... */
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)))
int
_metaphone(
/* IN */
char *word,
int max_phonemes,
/* OUT */
char **phoned_word
)
{
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);
if (!*phoned_word)
return META_ERROR;
}
else
{
*phoned_word = palloc(sizeof(char) * max_phonemes + 1);
if (!*phoned_word)
return META_ERROR;
}
/*-- 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 = _textout(PG_GETARG_TEXT_P(0));
_soundex(arg, outstr);
PG_RETURN_TEXT_P(_textin(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;
}
}
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