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7b1f6ffaab
> Second argument to metaphone is suposed to set the limit on the > number of characters to return, but it breaks on some phrases: > > usps=# select metaphone(a,3),metaphone(a,4),metaphone(a,20) from > (select 'Hello world'::varchar AS a) a; > HLW | HLWR | HLWRLT > > usps=# select metaphone(a,3),metaphone(a,4),metaphone(a,20) from > (select 'A A COMEAUX MEMORIAL'::varchar AS a) a; > AKM | AKMKS | AKMKSMMRL > > In every case I've found that does this, the 4th and 5th letters are > always 'KS'. Nice catch. There was a bug in the original metaphone algorithm from CPAN. Patch attached (while I was at it I updated my email address, changed the copyright to PGDG, and removed an unnecessary palloc). Here's how it looks now: regression=# select metaphone(a,4) from (select 'A A COMEAUX MEMORIAL'::varchar AS a) a; metaphone ----------- AKMK (1 row) regression=# select metaphone(a,5) from (select 'A A COMEAUX MEMORIAL'::varchar AS a) a; metaphone ----------- AKMKS (1 row) Joe Conway
175 lines
5.1 KiB
C
175 lines
5.1 KiB
C
/*
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* fuzzystrmatch.h
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*
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* Functions for "fuzzy" comparison of strings
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*
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* Joe Conway <mail@joeconway.com>
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*
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* Copyright (c) 2001, 2002, 2003 by PostgreSQL Global Development Group
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* ALL RIGHTS RESERVED;
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*
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* levenshtein()
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* -------------
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* Written based on a description of the algorithm by Michael Gilleland
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* found at http://www.merriampark.com/ld.htm
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* Also looked at levenshtein.c in the PHP 4.0.6 distribution for
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* inspiration.
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*
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* metaphone()
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* -----------
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* Modified for PostgreSQL by Joe Conway.
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* Based on CPAN's "Text-Metaphone-1.96" by Michael G Schwern <schwern@pobox.com>
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* Code slightly modified for use as PostgreSQL function (palloc, elog, etc).
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* Metaphone was originally created by Lawrence Philips and presented in article
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* in "Computer Language" December 1990 issue.
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation for any purpose, without fee, and without a written agreement
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* is hereby granted, provided that the above copyright notice and this
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* paragraph and the following two paragraphs appear in all copies.
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*
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* IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
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* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
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* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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*/
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#ifndef FUZZYSTRMATCH_H
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#define FUZZYSTRMATCH_H
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#include "postgres.h"
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#include <ctype.h>
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#include "fmgr.h"
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#include "utils/builtins.h"
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/*
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* External declarations
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*/
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extern Datum levenshtein(PG_FUNCTION_ARGS);
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extern Datum metaphone(PG_FUNCTION_ARGS);
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extern Datum soundex(PG_FUNCTION_ARGS);
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/*
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* Soundex
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*/
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static void _soundex(const char *instr, char *outstr);
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#define SOUNDEX_LEN 4
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#define _textin(str) DirectFunctionCall1(textin, CStringGetDatum(str))
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#define _textout(str) DatumGetPointer(DirectFunctionCall1(textout, PointerGetDatum(str)))
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/* ABCDEFGHIJKLMNOPQRSTUVWXYZ */
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static const char *soundex_table = "01230120022455012623010202";
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#define soundex_code(letter) soundex_table[toupper((unsigned char) (letter)) - 'A']
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/*
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* Levenshtein
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*/
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#define STRLEN(p) strlen(p)
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#define CHAREQ(p1, p2) (*(p1) == *(p2))
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#define NextChar(p) ((p)++)
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#define MAX_LEVENSHTEIN_STRLEN 255
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/*
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* Metaphone
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*/
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#define MAX_METAPHONE_STRLEN 255
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/*
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* Original code by Michael G Schwern starts here.
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* Code slightly modified for use as PostgreSQL
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* function (combined *.h into here).
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*------------------------------------------------------------------*/
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/**************************************************************************
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metaphone -- Breaks english phrases down into their phonemes.
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Input
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word -- An english word to be phonized
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max_phonemes -- How many phonemes to calculate. If 0, then it
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will phonize the entire phrase.
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phoned_word -- The final phonized word. (We'll allocate the
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memory.)
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Output
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error -- A simple error flag, returns TRUE or FALSE
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NOTES: ALL non-alpha characters are ignored, this includes whitespace,
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although non-alpha characters will break up phonemes.
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****************************************************************************/
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/**************************************************************************
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my constants -- constants I like
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Probably redundant.
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***************************************************************************/
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#define META_ERROR FALSE
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#define META_SUCCESS TRUE
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#define META_FAILURE FALSE
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/* I add modifications to the traditional metaphone algorithm that you
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might find in books. Define this if you want metaphone to behave
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traditionally */
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#undef USE_TRADITIONAL_METAPHONE
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/* Special encodings */
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#define SH 'X'
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#define TH '0'
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char Lookahead(char *word, int how_far);
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int
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_metaphone(
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/* IN */
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char *word,
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int max_phonemes,
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/* OUT */
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char **phoned_word
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);
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/* Metachar.h ... little bits about characters for metaphone */
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/*-- Character encoding array & accessing macros --*/
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/* Stolen directly out of the book... */
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char _codes[26] = {
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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
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/* 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 */
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};
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#define ENCODE(c) (isalpha((unsigned char) (c)) ? _codes[((toupper((unsigned char) (c))) - 'A')] : 0)
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#define isvowel(c) (ENCODE(c) & 1) /* AEIOU */
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/* These letters are passed through unchanged */
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#define NOCHANGE(c) (ENCODE(c) & 2) /* FJMNR */
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/* These form dipthongs when preceding H */
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#define AFFECTH(c) (ENCODE(c) & 4) /* CGPST */
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/* These make C and G soft */
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#define MAKESOFT(c) (ENCODE(c) & 8) /* EIY */
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/* These prevent GH from becoming F */
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#define NOGHTOF(c) (ENCODE(c) & 16) /* BDH */
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#endif /* FUZZYSTRMATCH_H */
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