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Make dmetaphone collation-aware

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The dmetaphone() SQL function internally upper-cases the argument
string.  It did this using the toupper() function.  That way, it has a
dependency on the global LC_CTYPE locale setting, which we want to get
rid of.

The "double metaphone" algorithm specifically supports the "C with
cedilla" letter, so just using ASCII case conversion wouldn't work.

To fix that, use the passed-in collation and use the str_toupper()
function, which has full awareness of collations and collation
providers.

Note that this does not change the fact that this function only works
correctly with single-byte encodings.  The change to str_toupper()
makes the case conversion multibyte-enabled, but the rest of the
function is still not ready.

Reviewed-by: Jeff Davis <pgsql@j-davis.com>
Discussion: https://www.postgresql.org/message-id/108e07a2-0632-4f00-984d-fe0e0d0ec726%40eisentraut.org
This commit is contained in:
Peter Eisentraut
2026-01-12 08:35:48 +01:00
parent 5d1f5079ab
commit e39ece0343
1 changed files with 16 additions and 11 deletions
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27
contrib/fuzzystrmatch/dmetaphone.c
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@ -99,6 +99,7 @@ The remaining code is authored by Andrew Dunstan <amdunstan@ncshp.org> and
#include "postgres.h"
#include "utils/builtins.h"
#include "utils/formatting.h"
/* turn off assertions for embedded function */
#define NDEBUG
@ -117,7 +118,7 @@ The remaining code is authored by Andrew Dunstan <amdunstan@ncshp.org> and
#include <ctype.h>
/* prototype for the main function we got from the perl module */
static void DoubleMetaphone(char *str, char **codes);
static void DoubleMetaphone(const char *str, Oid collid, char **codes);
#ifndef DMETAPHONE_MAIN
@ -142,7 +143,7 @@ dmetaphone(PG_FUNCTION_ARGS)
arg = PG_GETARG_TEXT_PP(0);
aptr = text_to_cstring(arg);
DoubleMetaphone(aptr, codes);
DoubleMetaphone(aptr, PG_GET_COLLATION(), codes);
code = codes[0];
if (!code)
code = "";
@ -171,7 +172,7 @@ dmetaphone_alt(PG_FUNCTION_ARGS)
arg = PG_GETARG_TEXT_PP(0);
aptr = text_to_cstring(arg);
DoubleMetaphone(aptr, codes);
DoubleMetaphone(aptr, PG_GET_COLLATION(), codes);
code = codes[1];
if (!code)
code = "";
@ -278,13 +279,17 @@ IncreaseBuffer(metastring *s, int chars_needed)
}
static void
MakeUpper(metastring *s)
static metastring *
MakeUpper(metastring *s, Oid collid)
{
char *i;
char *newstr;
metastring *newms;
for (i = s->str; *i; i++)
*i = toupper((unsigned char) *i);
newstr = str_toupper(s->str, s->length, collid);
newms = NewMetaString(newstr);
DestroyMetaString(s);
return newms;
}
@ -392,7 +397,7 @@ MetaphAdd(metastring *s, const char *new_str)
static void
DoubleMetaphone(char *str, char **codes)
DoubleMetaphone(const char *str, Oid collid, char **codes)
{
int length;
metastring *original;
@ -414,7 +419,7 @@ DoubleMetaphone(char *str, char **codes)
primary->free_string_on_destroy = 0;
secondary->free_string_on_destroy = 0;
MakeUpper(original);
original = MakeUpper(original, collid);
/* skip these when at start of word */
if (StringAt(original, 0, 2, "GN", "KN", "PN", "WR", "PS", ""))
@ -1430,7 +1435,7 @@ main(int argc, char **argv)
if (argc > 1)
{
DoubleMetaphone(argv[1], codes);
DoubleMetaphone(argv[1], DEFAULT_COLLATION_OID, codes);
printf("%s|%s\n", codes[0], codes[1]);
}
}