postgresql/contrib/fuzzystrmatch

/*
 * fuzzystrmatch.c
 *
 * Functions for "fuzzy" comparison of strings
 *
 * Copyright (c) Joseph Conway <joseph.conway@home.com>, 2001;
 *
 * 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.
 *
 */


Version 0.1 (3 August, 2001):
  Functions to calculate the degree to which two strings match in a "fuzzy" way
  Tested under Linux (Red Hat 6.2 and 7.0) and PostgreSQL 7.2devel

Release Notes:

  Version 0.1
    - initial release    

Installation:
  Place these files in a directory called 'fuzzystrmatch' under 'contrib' in the PostgreSQL source tree. Then run:

    make
    make install

  You can use fuzzystrmatch.sql to create the functions in your database of choice, e.g.

    psql -U postgres template1 < fuzzystrmatch.sql

  installs following functions into database template1:

     levenshtein() - calculates the levenshtein distance between two strings
     metaphone() - calculates the metaphone code of an input string

Documentation
==================================================================
Name

levenshtein -- calculates the levenshtein distance between two strings

Synopsis

levenshtein(text source, text target)

Inputs

  source
    any text string, 255 characters max, NOT NULL

  target
    any text string, 255 characters max, NOT NULL

Outputs

  Returns int

Example usage

  select levenshtein('GUMBO','GAMBOL');

==================================================================
Name

metaphone -- calculates the metaphone code of an input string

Synopsis

metaphone(text source, int max_output_length)

Inputs

  source
    any text string, 255 characters max, NOT NULL

  max_output_length
    maximum length of the output metaphone code; if longer, the output
    is truncated to this length

Outputs

  Returns text

Example usage

  select metaphone('GUMBO',4);

==================================================================
-- Joe Conway