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Subject: Re: Remaining dependency on setlocale()
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <83F6E6A9-FF29-41C9-9E15-EA5360E912D0@gmail.com>
Date: Thu, 27 Nov 2025 09:08:16 +0800
Cc: Peter Eisentraut <peter@eisentraut.org>,
 Thomas Munro <thomas.munro@gmail.com>,
 Tom Lane <tgl@sss.pgh.pa.us>,
 pgsql-hackers@postgresql.org
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> On Nov 26, 2025, at 09:50, Chao Li <li.evan.chao@gmail.com> wrote:
>=20
> I will review the rest 3 commits tomorrow.

10 - 0009
```
 {
 	if (isalpha((unsigned char) c))
 	{
-		c =3D toupper((unsigned char) c);
+		c =3D pg_ascii_toupper((unsigned char) c);
```

Just curious. As isaplha() and toupper() come from the same header file =
ctype.h, if we replace toupper with pg_ascii_toupper, does isapha also =
need to be handled?

11 - 0010
```
-	for (i =3D 0; i < len; i++)
-	{
-		unsigned char ch =3D (unsigned char) ident[i];
+	dstsize =3D len + 1;
+	result =3D palloc(dstsize);
=20
-		if (ch >=3D 'A' && ch <=3D 'Z')
-			ch +=3D 'a' - 'A';
-		else if (enc_is_single_byte && IS_HIGHBIT_SET(ch) && =
isupper(ch))
-			ch =3D tolower(ch);
-		result[i] =3D (char) ch;
-	}
-	result[i] =3D '\0';
+	needed =3D pg_strfold_ident(result, dstsize, ident, len);
+	Assert(needed + 1 =3D=3D dstsize);
+	Assert(needed =3D=3D len);
```

I think assert both dstsize and len are redundant, because =
dstsize=3Dlen+1, and no place to change their values.

12 - 0010
```
+/*
+ * Fold an identifier using the database default locale.
+ *
+ * For historical reasons, does not use ordinary locale behavior. =
Should only
+ * be used for identifier folding. XXX: can we make this equivalent to
+ * pg_strfold(..., default_locale)?
+ */
+size_t
+pg_strfold_ident(char *dest, size_t destsize, const char *src, ssize_t =
srclen)
+{
+	if (default_locale =3D=3D NULL || default_locale->ctype =3D=3D =
NULL)
+	{
+		int			i;
+
+		for (i =3D 0; i < srclen && i < destsize; i++)
+		{
+			unsigned char ch =3D (unsigned char) src[i];
+
+			if (ch >=3D 'A' && ch <=3D 'Z')
+				ch +=3D 'a' - 'A';
+			dest[i] =3D (char) ch;
+		}
+
+		if (i < destsize)
+			dest[i] =3D '\0';
+
+		return srclen;
+	}
+	return default_locale->ctype->strfold_ident(dest, destsize, src, =
srclen,
+										=
		default_locale);
+}
```

Given default_local can be NULL only at some specific moment, can we do =
something like

Local =3D default_local;
If (local =3D=3D NULL || local->ctype =3D=3D NULL)
  Local =3D libc or other fallback;
Return default_locale->ctype->strfold_ident(dest, destsize, src, srclen, =
local);

This way avoids the duplicate code.

13 - 0011
```
+{ name =3D> 'lc_collate', type =3D> 'string', context =3D> 'PGC_SUSET', =
group =3D> 'CLIENT_CONN_LOCALE',
+  short_desc =3D> 'Sets the locale for text ordering in extensions.',
```

I just feel the GUC name is very misleading. Without carefully reading =
the doc, users may very easy to consider lc_collate the system=E2=80=99s =
locale. If it only affects extensions, then let=E2=80=99s name it =
accordingly, for example, =E2=80=9Cextension_lc_collate=E2=80=9D, or =
=E2=80=9Clegacy_lc_collate=E2=80=9D.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/