diff --git a/src/backend/parser/scansup.c b/src/backend/parser/scansup.c
index cd9594226d6..8e7078f42c8 100644
--- a/src/backend/parser/scansup.c
+++ b/src/backend/parser/scansup.c
@@ -18,7 +18,6 @@
 
 #include "mb/pg_wchar.h"
 #include "parser/scansup.h"
-#include "utils/pg_locale.h"
 
 
 /*
@@ -47,22 +46,35 @@ char *
 downcase_identifier(const char *ident, int len, bool warn, bool truncate)
 {
 	char	   *result;
-	size_t		needed pg_attribute_unused();
+	int			i;
+	bool		enc_is_single_byte;
+
+	result = palloc(len + 1);
+	enc_is_single_byte = pg_database_encoding_max_length() == 1;
 
 	/*
-	 * Preserves string length.
-	 *
-	 * NB: if we decide to support Unicode-aware identifier case folding, then
-	 * we need to account for a change in string length.
+	 * SQL99 specifies Unicode-aware case normalization, which we don't yet
+	 * have the infrastructure for.  Instead we use tolower() to provide a
+	 * locale-aware translation.  However, there are some locales where this
+	 * is not right either (eg, Turkish may do strange things with 'i' and
+	 * 'I').  Our current compromise is to use tolower() for characters with
+	 * the high bit set, as long as they aren't part of a multi-byte
+	 * character, and use an ASCII-only downcasing for 7-bit characters.
 	 */
-	result = palloc(len + 1);
+	for (i = 0; i < len; i++)
+	{
+		unsigned char ch = (unsigned char) ident[i];
 
-	needed = pg_downcase_ident(result, len + 1, ident, len);
-	Assert(needed == len);
-	Assert(result[len] == '\0');
+		if (ch >= 'A' && ch <= 'Z')
+			ch += 'a' - 'A';
+		else if (enc_is_single_byte && IS_HIGHBIT_SET(ch) && isupper(ch))
+			ch = tolower(ch);
+		result[i] = (char) ch;
+	}
+	result[i] = '\0';
 
-	if (len >= NAMEDATALEN && truncate)
-		truncate_identifier(result, len, warn);
+	if (i >= NAMEDATALEN && truncate)
+		truncate_identifier(result, i, warn);
 
 	return result;
 }
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index cca08ceac0b..88d2d54d388 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -1434,30 +1434,6 @@ pg_strfold(char *dst, size_t dstsize, const char *src, size_t srclen,
 		return locale->ctype->strfold(dst, dstsize, src, srclen, locale);
 }
 
-/*
- * pg_downcase_ident()
- *
- * Lowercase an identifier using historical identifier-folding semantics, and
- * return the result length (not including terminating NUL). If the result
- * length is less than dstsize, the NUL-terminated result is stored in dst;
- * otherwise the contents of dst are undefined.
- *
- * XXX: callers currently depend on the result length being equal to srclen,
- * but that may change in the future if we change to proper case folding.
- */
-size_t
-pg_downcase_ident(char *dst, size_t dstsize, const char *src, size_t srclen)
-{
-	pg_locale_t locale = default_locale;
-
-	if (locale == NULL || locale->ctype == NULL ||
-		locale->ctype->downcase_ident == NULL)
-		return strlower_c(dst, dstsize, src, srclen);
-	else
-		return locale->ctype->downcase_ident(dst, dstsize, src, srclen,
-											 locale);
-}
-
 /*
  * pg_strcoll
  *
diff --git a/src/backend/utils/adt/pg_locale_builtin.c b/src/backend/utils/adt/pg_locale_builtin.c
index 8fa0b637b06..184d35f9360 100644
--- a/src/backend/utils/adt/pg_locale_builtin.c
+++ b/src/backend/utils/adt/pg_locale_builtin.c
@@ -219,8 +219,6 @@ static const struct ctype_methods ctype_methods_builtin = {
 	.strtitle = strtitle_builtin,
 	.strupper = strupper_builtin,
 	.strfold = strfold_builtin,
-	/* uses plain ASCII semantics for historical reasons */
-	.downcase_ident = NULL,
 	.wc_isdigit = wc_isdigit_builtin,
 	.wc_isalpha = wc_isalpha_builtin,
 	.wc_isalnum = wc_isalnum_builtin,
diff --git a/src/backend/utils/adt/pg_locale_icu.c b/src/backend/utils/adt/pg_locale_icu.c
index c35b9edc652..d0081264ea5 100644
--- a/src/backend/utils/adt/pg_locale_icu.c
+++ b/src/backend/utils/adt/pg_locale_icu.c
@@ -72,8 +72,6 @@ static size_t strupper_icu_utf8(char *dest, size_t destsize, const char *src,
 								size_t srclen, pg_locale_t locale);
 static size_t strfold_icu_utf8(char *dest, size_t destsize, const char *src,
 							   size_t srclen, pg_locale_t locale);
-static size_t downcase_ident_icu(char *dst, size_t dstsize, const char *src,
-								 size_t srclen, pg_locale_t locale);
 static int	strncoll_icu(const char *arg1, size_t len1,
 						 const char *arg2, size_t len2,
 						 pg_locale_t locale);
@@ -145,7 +143,7 @@ static int32_t foldcase_options(const char *locale);
 
 /*
  * XXX: many of the functions below rely on casts directly from pg_wchar to
- * UChar32, which is correct for UTF-8 and LATIN1, but not in general.
+ * UChar32, which is correct for the UTF-8 encoding, but not in general.
  */
 
 static pg_wchar
@@ -270,7 +268,6 @@ static const struct ctype_methods ctype_methods_icu = {
 	.strtitle = strtitle_icu,
 	.strupper = strupper_icu,
 	.strfold = strfold_icu,
-	.downcase_ident = downcase_ident_icu,
 	.wc_isdigit = wc_isdigit_icu,
 	.wc_isalpha = wc_isalpha_icu,
 	.wc_isalnum = wc_isalnum_icu,
@@ -291,8 +288,6 @@ static const struct ctype_methods ctype_methods_icu_utf8 = {
 	.strtitle = strtitle_icu_utf8,
 	.strupper = strupper_icu_utf8,
 	.strfold = strfold_icu_utf8,
-	/* uses plain ASCII semantics for historical reasons */
-	.downcase_ident = NULL,
 	.wc_isdigit = wc_isdigit_icu,
 	.wc_isalpha = wc_isalpha_icu,
 	.wc_isalnum = wc_isalnum_icu,
@@ -308,28 +303,6 @@ static const struct ctype_methods ctype_methods_icu_utf8 = {
 	.wc_tolower = tolower_icu,
 };
 
-/*
- * ICU still depends on libc for compatibility with certain historical
- * behavior for single-byte encodings.  See downcase_ident_icu().
- *
- * XXX: consider fixing by decoding the single byte into a code point, and
- * using u_tolower().
- */
-static locale_t
-make_libc_ctype_locale(const char *ctype)
-{
-	locale_t	loc;
-
-#ifndef WIN32
-	loc = newlocale(LC_CTYPE_MASK, ctype, NULL);
-#else
-	loc = _create_locale(LC_ALL, ctype);
-#endif
-	if (!loc)
-		report_newlocale_failure(ctype);
-
-	return loc;
-}
 #endif
 
 pg_locale_t
@@ -340,7 +313,6 @@ create_pg_locale_icu(Oid collid, MemoryContext context)
 	const char *iculocstr;
 	const char *icurules = NULL;
 	UCollator  *collator;
-	locale_t	loc = (locale_t) 0;
 	pg_locale_t result;
 
 	if (collid == DEFAULT_COLLATION_OID)
@@ -363,18 +335,6 @@ create_pg_locale_icu(Oid collid, MemoryContext context)
 		if (!isnull)
 			icurules = TextDatumGetCString(datum);
 
-		/* libc only needed for default locale and single-byte encoding */
-		if (pg_database_encoding_max_length() == 1)
-		{
-			const char *ctype;
-
-			datum = SysCacheGetAttrNotNull(DATABASEOID, tp,
-										   Anum_pg_database_datctype);
-			ctype = TextDatumGetCString(datum);
-
-			loc = make_libc_ctype_locale(ctype);
-		}
-
 		ReleaseSysCache(tp);
 	}
 	else
@@ -405,7 +365,6 @@ create_pg_locale_icu(Oid collid, MemoryContext context)
 	result = MemoryContextAllocZero(context, sizeof(struct pg_locale_struct));
 	result->icu.locale = MemoryContextStrdup(context, iculocstr);
 	result->icu.ucol = collator;
-	result->icu.lt = loc;
 	result->deterministic = deterministic;
 	result->collate_is_c = false;
 	result->ctype_is_c = false;
@@ -716,39 +675,6 @@ strfold_icu_utf8(char *dest, size_t destsize, const char *src, size_t srclen,
 	return needed;
 }
 
-/*
- * For historical compatibility, behavior is not multibyte-aware.
- *
- * NB: uses libc tolower_l() for single-byte encodings (also for historical
- * compatibility), and therefore relies on the LC_CTYPE setting.
- */
-static size_t
-downcase_ident_icu(char *dst, size_t dstsize, const char *src,
-				   size_t srclen, pg_locale_t locale)
-{
-	size_t		i;
-	bool		libc_lower;
-	locale_t	lt = locale->icu.lt;
-
-	libc_lower = lt && (pg_database_encoding_max_length() == 1);
-
-	for (i = 0; i < srclen && i < dstsize; i++)
-	{
-		unsigned char ch = (unsigned char) src[i];
-
-		if (ch >= 'A' && ch <= 'Z')
-			ch = pg_ascii_tolower(ch);
-		else if (libc_lower && IS_HIGHBIT_SET(ch) && isupper_l(ch, lt))
-			ch = tolower_l(ch, lt);
-		dst[i] = (char) ch;
-	}
-
-	if (i < dstsize)
-		dst[i] = '\0';
-
-	return srclen;
-}
-
 /*
  * strncoll_icu_utf8()
  *
diff --git a/src/backend/utils/adt/pg_locale_libc.c b/src/backend/utils/adt/pg_locale_libc.c
index 7348ed90fc3..02c419aa62a 100644
--- a/src/backend/utils/adt/pg_locale_libc.c
+++ b/src/backend/utils/adt/pg_locale_libc.c
@@ -390,41 +390,12 @@ tolower_libc_mb(pg_wchar wc, pg_locale_t locale)
 		return wc;
 }
 
-/*
- * Characters A..Z always downcase to a..z, even in the Turkish
- * locale. Characters beyond 127 use tolower().
- */
-static size_t
-downcase_ident_libc_sb(char *dst, size_t dstsize, const char *src,
-					   size_t srclen, pg_locale_t locale)
-{
-	locale_t	loc = locale->lt;
-	size_t		i;
-
-	for (i = 0; i < srclen && i < dstsize; i++)
-	{
-		unsigned char ch = (unsigned char) src[i];
-
-		if (ch >= 'A' && ch <= 'Z')
-			ch = pg_ascii_tolower(ch);
-		else if (IS_HIGHBIT_SET(ch) && isupper_l(ch, loc))
-			ch = tolower_l(ch, loc);
-		dst[i] = (char) ch;
-	}
-
-	if (i < dstsize)
-		dst[i] = '\0';
-
-	return srclen;
-}
-
 static const struct ctype_methods ctype_methods_libc_sb = {
 	.strlower = strlower_libc_sb,
 	.strtitle = strtitle_libc_sb,
 	.strupper = strupper_libc_sb,
 	/* in libc, casefolding is the same as lowercasing */
 	.strfold = strlower_libc_sb,
-	.downcase_ident = downcase_ident_libc_sb,
 	.wc_isdigit = wc_isdigit_libc_sb,
 	.wc_isalpha = wc_isalpha_libc_sb,
 	.wc_isalnum = wc_isalnum_libc_sb,
@@ -451,8 +422,6 @@ static const struct ctype_methods ctype_methods_libc_other_mb = {
 	.strupper = strupper_libc_mb,
 	/* in libc, casefolding is the same as lowercasing */
 	.strfold = strlower_libc_mb,
-	/* uses plain ASCII semantics for historical reasons */
-	.downcase_ident = NULL,
 	.wc_isdigit = wc_isdigit_libc_sb,
 	.wc_isalpha = wc_isalpha_libc_sb,
 	.wc_isalnum = wc_isalnum_libc_sb,
@@ -474,8 +443,6 @@ static const struct ctype_methods ctype_methods_libc_utf8 = {
 	.strupper = strupper_libc_mb,
 	/* in libc, casefolding is the same as lowercasing */
 	.strfold = strlower_libc_mb,
-	/* uses plain ASCII semantics for historical reasons */
-	.downcase_ident = NULL,
 	.wc_isdigit = wc_isdigit_libc_mb,
 	.wc_isalpha = wc_isalpha_libc_mb,
 	.wc_isalnum = wc_isalnum_libc_mb,
diff --git a/src/include/utils/pg_locale.h b/src/include/utils/pg_locale.h
index fcd508f5dd6..36cd22dd255 100644
--- a/src/include/utils/pg_locale.h
+++ b/src/include/utils/pg_locale.h
@@ -116,11 +116,6 @@ struct ctype_methods
 							const char *src, size_t srclen,
 							pg_locale_t locale);
 
-	/* optional */
-	size_t		(*downcase_ident) (char *dest, size_t destsize,
-								   const char *src, size_t srclen,
-								   pg_locale_t locale);
-
 	/* required */
 	bool		(*wc_isdigit) (pg_wchar wc, pg_locale_t locale);
 	bool		(*wc_isalpha) (pg_wchar wc, pg_locale_t locale);
@@ -175,7 +170,6 @@ struct pg_locale_struct
 			const char *locale;
 			struct UCollator *ucol;
 			struct UCaseMap *ucasemap;
-			locale_t	lt;
 		}			icu;
 #endif
 	};
@@ -199,8 +193,6 @@ extern size_t pg_strupper(char *dst, size_t dstsize,
 extern size_t pg_strfold(char *dst, size_t dstsize,
 						 const char *src, size_t srclen,
 						 pg_locale_t locale);
-extern size_t pg_downcase_ident(char *dst, size_t dstsize,
-								const char *src, size_t srclen);
 extern int	pg_strcoll(const char *arg1, const char *arg2, pg_locale_t locale);
 extern int	pg_strncoll(const char *arg1, size_t len1,
 						const char *arg2, size_t len2, pg_locale_t locale);