Jim C. Nasby wrote:

> 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

Author: bmomjian

contrib/fuzzystrmatch/README.fuzzystrmatch

@@ -3,7 +3,10 @@
  *
  * Functions for "fuzzy" comparison of strings
  *
- * Copyright (c) Joseph Conway <joseph.conway@home.com>, 2001;
+ * Joe Conway <mail@joeconway.com>
+ *
+ * Copyright (c) 2001, 2002, 2003 by PostgreSQL Global Development Group
+ * ALL RIGHTS RESERVED;
  *
  * levenshtein()
  * -------------

contrib/fuzzystrmatch/fuzzystrmatch.c

@@ -3,7 +3,10 @@
  *
  * Functions for "fuzzy" comparison of strings
  *
- * Copyright (c) Joseph Conway <joseph.conway@home.com>, 2001;
+ * Joe Conway <mail@joeconway.com>
+ *
+ * Copyright (c) 2001, 2002, 2003 by PostgreSQL Global Development Group
+ * ALL RIGHTS RESERVED;
  *
  * levenshtein()
  * -------------
@@ -221,9 +224,6 @@ metaphone(PG_FUNCTION_ARGS)
 	if (!(reqlen > 0))
 		elog(ERROR, "metaphone: Requested Metaphone output length must be > 0");
 
-	metaph = palloc(reqlen);
-	memset(metaph, '\0', reqlen);
-
 	retval = _metaphone(str_i, reqlen, &metaph);
 	if (retval == META_SUCCESS)
 	{
@@ -629,7 +629,8 @@ _metaphone(
 				/* KS */
 			case 'X':
 				Phonize('K');
-				Phonize('S');
+				if (max_phonemes == 0 || Phone_Len < max_phonemes)
+					Phonize('S');
 				break;
 				/* Y if followed by a vowel */
 			case 'Y':

contrib/fuzzystrmatch/fuzzystrmatch.h

@@ -3,7 +3,10 @@
  *
  * Functions for "fuzzy" comparison of strings
  *
- * Copyright (c) Joseph Conway <joseph.conway@home.com>, 2001;
+ * Joe Conway <mail@joeconway.com>
+ *
+ * Copyright (c) 2001, 2002, 2003 by PostgreSQL Global Development Group
+ * ALL RIGHTS RESERVED;
  *
  * levenshtein()
  * -------------