Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 792 insertions, 0 deletions

diff --git a/contrib/fuzzystrmatch/fuzzystrmatch.c b/contrib/fuzzystrmatch/fuzzystrmatch.c
new file mode 100644
index 0000000..d237772
--- /dev/null
+++ b/contrib/fuzzystrmatch/fuzzystrmatch.c
@@ -0,0 +1,792 @@
+/*
+ * fuzzystrmatch.c
+ *
+ * Functions for "fuzzy" comparison of strings
+ *
+ * Joe Conway <mail@joeconway.com>
+ *
+ * contrib/fuzzystrmatch/fuzzystrmatch.c
+ * Copyright (c) 2001-2021, PostgreSQL Global Development Group
+ * ALL RIGHTS RESERVED;
+ *
+ * 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 "mb/pg_wchar.h"
+#include "utils/builtins.h"
+#include "utils/varlena.h"
+
+PG_MODULE_MAGIC;
+
+/*
+ * Soundex
+ */
+static void _soundex(const char *instr, char *outstr);
+
+#define SOUNDEX_LEN 4
+
+/*									ABCDEFGHIJKLMNOPQRSTUVWXYZ */
+static const char *soundex_table = "01230120022455012623010202";
+
+static char
+soundex_code(char letter)
+{
+	letter = toupper((unsigned char) letter);
+	/* Defend against non-ASCII letters */
+	if (letter >= 'A' && letter <= 'Z')
+		return soundex_table[letter - 'A'];
+	return letter;
+}
+
+/*
+ * 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.
+****************************************************************************/
+
+
+/*	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 void _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... */
+static const 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 */
+};
+
+static int
+getcode(char c)
+{
+	if (isalpha((unsigned char) c))
+	{
+		c = toupper((unsigned char) c);
+		/* Defend against non-ASCII letters */
+		if (c >= 'A' && c <= 'Z')
+			return _codes[c - 'A'];
+	}
+	return 0;
+}
+
+#define isvowel(c)	(getcode(c) & 1)	/* AEIOU */
+
+/* These letters are passed through unchanged */
+#define NOCHANGE(c) (getcode(c) & 2)	/* FJMNR */
+
+/* These form diphthongs when preceding H */
+#define AFFECTH(c)	(getcode(c) & 4)	/* CGPST */
+
+/* These make C and G soft */
+#define MAKESOFT(c) (getcode(c) & 8)	/* EIY */
+
+/* These prevent GH from becoming F */
+#define NOGHTOF(c)	(getcode(c) & 16)	/* BDH */
+
+PG_FUNCTION_INFO_V1(levenshtein_with_costs);
+Datum
+levenshtein_with_costs(PG_FUNCTION_ARGS)
+{
+	text	   *src = PG_GETARG_TEXT_PP(0);
+	text	   *dst = PG_GETARG_TEXT_PP(1);
+	int			ins_c = PG_GETARG_INT32(2);
+	int			del_c = PG_GETARG_INT32(3);
+	int			sub_c = PG_GETARG_INT32(4);
+	const char *s_data;
+	const char *t_data;
+	int			s_bytes,
+				t_bytes;
+
+	/* Extract a pointer to the actual character data */
+	s_data = VARDATA_ANY(src);
+	t_data = VARDATA_ANY(dst);
+	/* Determine length of each string in bytes */
+	s_bytes = VARSIZE_ANY_EXHDR(src);
+	t_bytes = VARSIZE_ANY_EXHDR(dst);
+
+	PG_RETURN_INT32(varstr_levenshtein(s_data, s_bytes, t_data, t_bytes,
+									   ins_c, del_c, sub_c, false));
+}
+
+
+PG_FUNCTION_INFO_V1(levenshtein);
+Datum
+levenshtein(PG_FUNCTION_ARGS)
+{
+	text	   *src = PG_GETARG_TEXT_PP(0);
+	text	   *dst = PG_GETARG_TEXT_PP(1);
+	const char *s_data;
+	const char *t_data;
+	int			s_bytes,
+				t_bytes;
+
+	/* Extract a pointer to the actual character data */
+	s_data = VARDATA_ANY(src);
+	t_data = VARDATA_ANY(dst);
+	/* Determine length of each string in bytes */
+	s_bytes = VARSIZE_ANY_EXHDR(src);
+	t_bytes = VARSIZE_ANY_EXHDR(dst);
+
+	PG_RETURN_INT32(varstr_levenshtein(s_data, s_bytes, t_data, t_bytes,
+									   1, 1, 1, false));
+}
+
+
+PG_FUNCTION_INFO_V1(levenshtein_less_equal_with_costs);
+Datum
+levenshtein_less_equal_with_costs(PG_FUNCTION_ARGS)
+{
+	text	   *src = PG_GETARG_TEXT_PP(0);
+	text	   *dst = PG_GETARG_TEXT_PP(1);
+	int			ins_c = PG_GETARG_INT32(2);
+	int			del_c = PG_GETARG_INT32(3);
+	int			sub_c = PG_GETARG_INT32(4);
+	int			max_d = PG_GETARG_INT32(5);
+	const char *s_data;
+	const char *t_data;
+	int			s_bytes,
+				t_bytes;
+
+	/* Extract a pointer to the actual character data */
+	s_data = VARDATA_ANY(src);
+	t_data = VARDATA_ANY(dst);
+	/* Determine length of each string in bytes */
+	s_bytes = VARSIZE_ANY_EXHDR(src);
+	t_bytes = VARSIZE_ANY_EXHDR(dst);
+
+	PG_RETURN_INT32(varstr_levenshtein_less_equal(s_data, s_bytes,
+												  t_data, t_bytes,
+												  ins_c, del_c, sub_c,
+												  max_d, false));
+}
+
+
+PG_FUNCTION_INFO_V1(levenshtein_less_equal);
+Datum
+levenshtein_less_equal(PG_FUNCTION_ARGS)
+{
+	text	   *src = PG_GETARG_TEXT_PP(0);
+	text	   *dst = PG_GETARG_TEXT_PP(1);
+	int			max_d = PG_GETARG_INT32(2);
+	const char *s_data;
+	const char *t_data;
+	int			s_bytes,
+				t_bytes;
+
+	/* Extract a pointer to the actual character data */
+	s_data = VARDATA_ANY(src);
+	t_data = VARDATA_ANY(dst);
+	/* Determine length of each string in bytes */
+	s_bytes = VARSIZE_ANY_EXHDR(src);
+	t_bytes = VARSIZE_ANY_EXHDR(dst);
+
+	PG_RETURN_INT32(varstr_levenshtein_less_equal(s_data, s_bytes,
+												  t_data, t_bytes,
+												  1, 1, 1,
+												  max_d, false));
+}
+
+
+/*
+ * 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;
+
+	/* 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)));
+
+	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")));
+
+	_metaphone(str_i, reqlen, &metaph);
+	PG_RETURN_TEXT_P(cstring_to_text(metaph));
+}
+
+
+/*
+ * 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 void
+_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;
+		}
+	}
+
+	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;
+}								/* 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_PP(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_PP(0)), sndx1);
+	_soundex(text_to_cstring(PG_GETARG_TEXT_PP(1)), sndx2);
+
+	result = 0;
+	for (i = 0; i < SOUNDEX_LEN; i++)
+	{
+		if (sndx1[i] == sndx2[i])
+			result++;
+	}
+
+	PG_RETURN_INT32(result);
+}