v28-0002-Support-PG_UNICODE_FAST-locale-in-the-builtin-co.patch

From d4c92a7f9e804f228c9d92881003305e68ebab69 Mon Sep 17 00:00:00 2001
From: Jeff Davis <jeff@j-davis.com>
Date: Wed, 6 Mar 2024 18:15:33 -0800
Subject: [PATCH v28 2/2] Support PG_UNICODE_FAST locale in the builtin
 collation provider.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

------ CATVERSION ------

The PG_UNICODE_FAST locale uses code point sort order (fast,
memcmp-based) combined with Unicode character semantics. The character
semantics are based on Unicode full case mapping.

Full case mapping can map a single codepoint to multiple codepoints,
such as "ß" uppercasing to "SS". Additionally, it handles
context-sensitive mappings like the "final sigma", and it uses
titlecase mappings such as "Dž" when titlecasing (rather than plain
uppercase mappings).

Importantly, the uppercasing of "ß" as "SS" is specifically mentioned
by the SQL standard. In Postgres, UCS_BASIC uses plain ASCII semantics
for case mapping and pattern matching, so if we changed it to use the
PG_UNICODE_FAST locale, it would offer better compliance with the
standard. For now, though, do not change the behavior of UCS_BASIC.

Discussion: https://postgr.es/m/27bb0e52-801d-4f73-a0a4-02cfdd4a9ada@eisentraut.org
---
 doc/src/sgml/charset.sgml                  |  17 +++
 doc/src/sgml/ref/create_collation.sgml     |   3 +-
 doc/src/sgml/ref/create_database.sgml      |   6 +-
 doc/src/sgml/ref/initdb.sgml               |   4 +-
 src/backend/regex/regc_pg_locale.c         |  11 +-
 src/backend/utils/adt/formatting.c         |  22 ++-
 src/backend/utils/adt/pg_locale.c          |  10 +-
 src/backend/utils/init/postinit.c          |   1 +
 src/bin/initdb/initdb.c                    |   6 +-
 src/include/catalog/pg_collation.dat       |   3 +
 src/include/utils/pg_locale.h              |   1 +
 src/test/regress/expected/collate.utf8.out | 160 +++++++++++++++++++++
 src/test/regress/sql/collate.utf8.sql      |  60 ++++++++
 13 files changed, 287 insertions(+), 17 deletions(-)

diff --git a/doc/src/sgml/charset.sgml b/doc/src/sgml/charset.sgml
index 55bbb20dac..fc520138a6 100644
--- a/doc/src/sgml/charset.sgml
+++ b/doc/src/sgml/charset.sgml
@@ -886,6 +886,23 @@ SELECT * FROM test1 ORDER BY a || b COLLATE "fr_FR";
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><literal>pg_unicode_fast</literal></term>
+      <listitem>
+       <para>
+        This collation sorts by Unicode code point values rather than natural
+        language order.  For the functions <function>lower</function>,
+        <function>initcap</function>, and <function>upper</function> it uses
+        Unicode full case mapping. For pattern matching (including regular
+        expressions), it uses the Standard variant of Unicode <ulink
+        url="https://www.unicode.org/reports/tr18/#Compatibility_Properties">Compatibility
+        Properties</ulink>.  Behavior is efficient and stable within a
+        <productname>Postgres</productname> major version.  It is only
+        available for encoding <literal>UTF8</literal>.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><literal>pg_c_utf8</literal></term>
       <listitem>
diff --git a/doc/src/sgml/ref/create_collation.sgml b/doc/src/sgml/ref/create_collation.sgml
index 85f18cbbe5..4c03e25d02 100644
--- a/doc/src/sgml/ref/create_collation.sgml
+++ b/doc/src/sgml/ref/create_collation.sgml
@@ -99,7 +99,8 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replace
       <para>
        If <replaceable>provider</replaceable> is <literal>builtin</literal>,
        then <replaceable>locale</replaceable> must be specified and set to
-       either <literal>C</literal> or <literal>C.UTF-8</literal>.
+       either <literal>C</literal>, <literal>C.UTF-8</literal> or
+       <literal>PG_UNICODE_FAST</literal>.
       </para>
      </listitem>
     </varlistentry>
diff --git a/doc/src/sgml/ref/create_database.sgml b/doc/src/sgml/ref/create_database.sgml
index 7653cb902e..a4b052ba08 100644
--- a/doc/src/sgml/ref/create_database.sgml
+++ b/doc/src/sgml/ref/create_database.sgml
@@ -168,7 +168,8 @@ CREATE DATABASE <replaceable class="parameter">name</replaceable>
         If <xref linkend="create-database-locale-provider"/> is
         <literal>builtin</literal>, then <replaceable>locale</replaceable> or
         <replaceable>builtin_locale</replaceable> must be specified and set to
-        either <literal>C</literal> or <literal>C.UTF-8</literal>.
+        either <literal>C</literal>, <literal>C.UTF-8</literal>, or
+        <literal>PG_UNICODE_FAST</literal>.
        </para>
        <tip>
         <para>
@@ -233,7 +234,8 @@ CREATE DATABASE <replaceable class="parameter">name</replaceable>
        </para>
        <para>
         The locales available for the <literal>builtin</literal> provider are
-        <literal>C</literal> and <literal>C.UTF-8</literal>.
+        <literal>C</literal>, <literal>C.UTF-8</literal> and
+        <literal>PG_UNICODE_FAST</literal>.
        </para>
       </listitem>
      </varlistentry>
diff --git a/doc/src/sgml/ref/initdb.sgml b/doc/src/sgml/ref/initdb.sgml
index dc9011b40e..dd15de82f6 100644
--- a/doc/src/sgml/ref/initdb.sgml
+++ b/doc/src/sgml/ref/initdb.sgml
@@ -289,8 +289,8 @@ PostgreSQL documentation
        <para>
         If <option>--locale-provider</option> is <literal>builtin</literal>,
         <option>--locale</option> or <option>--builtin-locale</option> must be
-        specified and set to <literal>C</literal> or
-        <literal>C.UTF-8</literal>.
+        specified and set to <literal>C</literal>, <literal>C.UTF-8</literal>
+        or <literal>PG_UNICODE_FAST</literal>.
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/backend/regex/regc_pg_locale.c b/src/backend/regex/regc_pg_locale.c
index 85f3238eb0..24c5200cef 100644
--- a/src/backend/regex/regc_pg_locale.c
+++ b/src/backend/regex/regc_pg_locale.c
@@ -78,6 +78,8 @@ static PG_Locale_Strategy pg_regex_strategy;
 static pg_locale_t pg_regex_locale;
 static Oid	pg_regex_collation;
 
+static bool regex_builtin_cclass_posix = false;
+
 /*
  * Hard-wired character properties for C locale
  */
@@ -271,7 +273,10 @@ pg_set_regex_collation(Oid collation)
 			if (pg_regex_locale)
 			{
 				if (pg_regex_locale->provider == COLLPROVIDER_BUILTIN)
+				{
 					pg_regex_strategy = PG_REGEX_BUILTIN;
+					regex_builtin_cclass_posix = !pg_regex_locale->info.builtin.casemap_full;
+				}
 				else
 					pg_regex_strategy = PG_REGEX_LOCALE_WIDE_L;
 			}
@@ -299,7 +304,7 @@ pg_wc_isdigit(pg_wchar c)
 			return (c <= (pg_wchar) 127 &&
 					(pg_char_properties[c] & PG_ISDIGIT));
 		case PG_REGEX_BUILTIN:
-			return pg_u_isdigit(c, true);
+			return pg_u_isdigit(c, regex_builtin_cclass_posix);
 		case PG_REGEX_LOCALE_WIDE:
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswdigit((wint_t) c);
@@ -367,7 +372,7 @@ pg_wc_isalnum(pg_wchar c)
 			return (c <= (pg_wchar) 127 &&
 					(pg_char_properties[c] & PG_ISALNUM));
 		case PG_REGEX_BUILTIN:
-			return pg_u_isalnum(c, true);
+			return pg_u_isalnum(c, regex_builtin_cclass_posix);
 		case PG_REGEX_LOCALE_WIDE:
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswalnum((wint_t) c);
@@ -546,7 +551,7 @@ pg_wc_ispunct(pg_wchar c)
 			return (c <= (pg_wchar) 127 &&
 					(pg_char_properties[c] & PG_ISPUNCT));
 		case PG_REGEX_BUILTIN:
-			return pg_u_ispunct(c, true);
+			return pg_u_ispunct(c, regex_builtin_cclass_posix);
 		case PG_REGEX_LOCALE_WIDE:
 			if (sizeof(wchar_t) >= 4 || c <= (pg_wchar) 0xFFFF)
 				return iswpunct((wint_t) c);
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index c2acc6c312..e591758c21 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -1695,13 +1695,15 @@ str_tolower(const char *buff, size_t nbytes, Oid collid)
 			dstsize = srclen + 1;
 			dst = palloc(dstsize);
 
-			needed = unicode_strlower(dst, dstsize, src, srclen, false);
+			needed = unicode_strlower(dst, dstsize, src, srclen,
+									  mylocale->info.builtin.casemap_full);
 			if (needed + 1 > dstsize)
 			{
 				/* grow buffer if needed and retry */
 				dstsize = needed + 1;
 				dst = repalloc(dst, dstsize);
-				needed = unicode_strlower(dst, dstsize, src, srclen, false);
+				needed = unicode_strlower(dst, dstsize, src, srclen,
+										  mylocale->info.builtin.casemap_full);
 				Assert(needed + 1 == dstsize);
 			}
 
@@ -1843,13 +1845,15 @@ str_toupper(const char *buff, size_t nbytes, Oid collid)
 			dstsize = srclen + 1;
 			dst = palloc(dstsize);
 
-			needed = unicode_strupper(dst, dstsize, src, srclen, false);
+			needed = unicode_strupper(dst, dstsize, src, srclen,
+									  mylocale->info.builtin.casemap_full);
 			if (needed + 1 > dstsize)
 			{
 				/* grow buffer if needed and retry */
 				dstsize = needed + 1;
 				dst = repalloc(dst, dstsize);
-				needed = unicode_strupper(dst, dstsize, src, srclen, false);
+				needed = unicode_strupper(dst, dstsize, src, srclen,
+										  mylocale->info.builtin.casemap_full);
 				Assert(needed + 1 == dstsize);
 			}
 
@@ -1929,6 +1933,7 @@ struct WordBoundaryState
 	size_t		offset;
 	bool		init;
 	bool		prev_alnum;
+	bool		posix;
 };
 
 /*
@@ -1945,7 +1950,7 @@ initcap_wbnext(void *state)
 	{
 		pg_wchar	u = utf8_to_unicode((unsigned char *) wbstate->str +
 										wbstate->offset);
-		bool		curr_alnum = pg_u_isalnum(u, true);
+		bool		curr_alnum = pg_u_isalnum(u, wbstate->posix);
 
 		if (!wbstate->init || curr_alnum != wbstate->prev_alnum)
 		{
@@ -2032,6 +2037,7 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 				.offset = 0,
 				.init = false,
 				.prev_alnum = false,
+				.posix = !mylocale->info.builtin.casemap_full,
 			};
 
 			Assert(GetDatabaseEncoding() == PG_UTF8);
@@ -2040,7 +2046,8 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 			dstsize = srclen + 1;
 			dst = palloc(dstsize);
 
-			needed = unicode_strtitle(dst, dstsize, src, srclen, false,
+			needed = unicode_strtitle(dst, dstsize, src, srclen,
+									  mylocale->info.builtin.casemap_full,
 									  initcap_wbnext, &wbstate);
 			if (needed + 1 > dstsize)
 			{
@@ -2051,7 +2058,8 @@ str_initcap(const char *buff, size_t nbytes, Oid collid)
 				/* grow buffer if needed and retry */
 				dstsize = needed + 1;
 				dst = repalloc(dst, dstsize);
-				needed = unicode_strtitle(dst, dstsize, src, srclen, false,
+				needed = unicode_strtitle(dst, dstsize, src, srclen,
+										  mylocale->info.builtin.casemap_full,
 										  initcap_wbnext, &wbstate);
 				Assert(needed + 1 == dstsize);
 			}
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index 377f5837a0..b6c96a6c39 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -1596,6 +1596,7 @@ pg_newlocale_from_collation(Oid collid)
 
 			result.info.builtin.locale = MemoryContextStrdup(TopMemoryContext,
 															 locstr);
+			result.info.builtin.casemap_full = (strcmp(locstr, "PG_UNICODE_FAST") == 0);
 		}
 		else if (collform->collprovider == COLLPROVIDER_LIBC)
 		{
@@ -1743,6 +1744,8 @@ get_collation_actual_version(char collprovider, const char *collcollate)
 			return "1";
 		else if (strcmp(collcollate, "C.UTF-8") == 0)
 			return "1";
+		else if (strcmp(collcollate, "PG_UNICODE_FAST") == 0)
+			return "1";
 		else
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -2528,9 +2531,12 @@ builtin_locale_encoding(const char *locale)
 {
 	if (strcmp(locale, "C") == 0)
 		return -1;
-	if (strcmp(locale, "C.UTF-8") == 0)
+	else if (strcmp(locale, "C.UTF-8") == 0)
+		return PG_UTF8;
+	else if (strcmp(locale, "PG_UNICODE_FAST") == 0)
 		return PG_UTF8;
 
+
 	ereport(ERROR,
 			(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 			 errmsg("invalid locale name \"%s\" for builtin provider",
@@ -2557,6 +2563,8 @@ builtin_validate_locale(int encoding, const char *locale)
 		canonical_name = "C";
 	else if (strcmp(locale, "C.UTF-8") == 0 || strcmp(locale, "C.UTF8") == 0)
 		canonical_name = "C.UTF-8";
+	else if (strcmp(locale, "PG_UNICODE_FAST") == 0)
+		canonical_name = "PG_UNICODE_FAST";
 
 	if (!canonical_name)
 		ereport(ERROR,
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 0805398e24..9a357e3f90 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -432,6 +432,7 @@ CheckMyDatabase(const char *name, bool am_superuser, bool override_allow_connect
 
 		default_locale.info.builtin.locale = MemoryContextStrdup(
 																 TopMemoryContext, datlocale);
+		default_locale.info.builtin.casemap_full = (strcmp(datlocale, "PG_UNICODE_FAST") == 0);
 	}
 	else if (dbform->datlocprovider == COLLPROVIDER_ICU)
 	{
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 30e17bd1d1..262a984d04 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -2408,6 +2408,8 @@ setlocales(void)
 		else if (strcmp(datlocale, "C.UTF-8") == 0 ||
 				 strcmp(datlocale, "C.UTF8") == 0)
 			canonname = "C.UTF-8";
+		else if (strcmp(datlocale, "PG_UNICODE_FAST") == 0)
+			canonname = "PG_UNICODE_FAST";
 		else
 			pg_fatal("invalid locale name \"%s\" for builtin provider",
 					 datlocale);
@@ -2704,7 +2706,9 @@ setup_locale_encoding(void)
 
 	if (locale_provider == COLLPROVIDER_BUILTIN)
 	{
-		if (strcmp(datlocale, "C.UTF-8") == 0 && encodingid != PG_UTF8)
+		if ((strcmp(datlocale, "C.UTF-8") == 0 ||
+			 strcmp(datlocale, "PG_UNICODE_FAST") == 0) &&
+			encodingid != PG_UTF8)
 			pg_fatal("builtin provider locale \"%s\" requires encoding \"%s\"",
 					 datlocale, "UTF-8");
 	}
diff --git a/src/include/catalog/pg_collation.dat b/src/include/catalog/pg_collation.dat
index dcf554bbd5..82a2fc582d 100644
--- a/src/include/catalog/pg_collation.dat
+++ b/src/include/catalog/pg_collation.dat
@@ -33,5 +33,8 @@
 { oid => '811', descr => 'sorts by Unicode code point; Unicode and POSIX character semantics',
   collname => 'pg_c_utf8', collprovider => 'b', collencoding => '6',
   colllocale => 'C.UTF-8', collversion => '1' },
+{ oid => '812', descr => 'sorts by Unicode code point; Unicode character semantics',
+  collname => 'pg_unicode_fast', collprovider => 'b', collencoding => '6',
+  colllocale => 'PG_UNICODE_FAST', collversion => '1' },
 
 ]
diff --git a/src/include/utils/pg_locale.h b/src/include/utils/pg_locale.h
index 205aa20067..03890000db 100644
--- a/src/include/utils/pg_locale.h
+++ b/src/include/utils/pg_locale.h
@@ -79,6 +79,7 @@ struct pg_locale_struct
 		struct
 		{
 			const char *locale;
+			bool		casemap_full;
 		}			builtin;
 		locale_t	lt;
 #ifdef USE_ICU
diff --git a/src/test/regress/expected/collate.utf8.out b/src/test/regress/expected/collate.utf8.out
index eff0ef21ac..63327a8fdd 100644
--- a/src/test/regress/expected/collate.utf8.out
+++ b/src/test/regress/expected/collate.utf8.out
@@ -134,3 +134,163 @@ SELECT 'δ' ~* '[Γ-Λ]' COLLATE PG_C_UTF8; -- same as above with cases reversed
  t
 (1 row)
 
+--
+-- Test PG_UNICODE_FAST
+--
+CREATE COLLATION regress_pg_unicode_fast (
+  provider = builtin, locale = 'unicode'); -- fails
+ERROR:  invalid locale name "unicode" for builtin provider
+CREATE COLLATION regress_pg_unicode_fast (
+  provider = builtin, locale = 'PG_UNICODE_FAST');
+CREATE TABLE test_pg_unicode_fast (
+  t TEXT COLLATE PG_UNICODE_FAST
+);
+INSERT INTO test_pg_unicode_fast VALUES
+  ('abc DEF 123abc'),
+  ('ábc sßs ßss DÉF'),
+  ('DŽxxDŽ džxxDž Džxxdž'),
+  ('ȺȺȺ'),
+  ('ⱥⱥⱥ'),
+  ('ⱥȺ');
+SELECT
+    t, lower(t), initcap(t), upper(t),
+    length(convert_to(t, 'UTF8')) AS t_bytes,
+    length(convert_to(lower(t), 'UTF8')) AS lower_t_bytes,
+    length(convert_to(initcap(t), 'UTF8')) AS initcap_t_bytes,
+    length(convert_to(upper(t), 'UTF8')) AS upper_t_bytes
+  FROM test_pg_unicode_fast;
+        t        |      lower      |     initcap      |       upper       | t_bytes | lower_t_bytes | initcap_t_bytes | upper_t_bytes 
+-----------------+-----------------+------------------+-------------------+---------+---------------+-----------------+---------------
+ abc DEF 123abc  | abc def 123abc  | Abc Def 123Abc   | ABC DEF 123ABC    |      14 |            14 |              14 |            14
+ ábc sßs ßss DÉF | ábc sßs ßss déf | Ábc Sßs Ssss Déf | ÁBC SSSS SSSS DÉF |      19 |            19 |              19 |            19
+ DŽxxDŽ džxxDž Džxxdž  | džxxdž džxxdž džxxdž  | Džxxdž Džxxdž Džxxdž   | DŽXXDŽ DŽXXDŽ DŽXXDŽ    |      20 |            20 |              20 |            20
+ ȺȺȺ             | ⱥⱥⱥ             | Ⱥⱥⱥ              | ȺȺȺ               |       6 |             9 |               8 |             6
+ ⱥⱥⱥ             | ⱥⱥⱥ             | Ⱥⱥⱥ              | ȺȺȺ               |       9 |             9 |               8 |             6
+ ⱥȺ              | ⱥⱥ              | Ⱥⱥ               | ȺȺ                |       5 |             6 |               5 |             4
+(6 rows)
+
+DROP TABLE test_pg_unicode_fast;
+-- test Final_Sigma
+SELECT lower('ΑΣ' COLLATE PG_UNICODE_FAST); -- 0391 03A3
+ lower 
+-------
+ ας
+(1 row)
+
+SELECT lower('ΑΣ0' COLLATE PG_UNICODE_FAST); -- 0391 03A3 0030
+ lower 
+-------
+ ας0
+(1 row)
+
+SELECT lower('ἈΣ̓' COLLATE PG_UNICODE_FAST); -- 0391 0343 03A3 0343
+ lower 
+-------
+ ἀς̓
+(1 row)
+
+SELECT lower('ᾼΣͅ' COLLATE PG_UNICODE_FAST); -- 0391 0345 03A3 0345
+ lower 
+-------
+ ᾳςͅ
+(1 row)
+
+-- test !Final_Sigma
+SELECT lower('Σ' COLLATE PG_UNICODE_FAST); -- 03A3
+ lower 
+-------
+ σ
+(1 row)
+
+SELECT lower('0Σ' COLLATE PG_UNICODE_FAST); -- 0030 03A3
+ lower 
+-------
+ 0σ
+(1 row)
+
+SELECT lower('ΑΣΑ' COLLATE PG_UNICODE_FAST); -- 0391 03A3 0391
+ lower 
+-------
+ ασα
+(1 row)
+
+SELECT lower('ἈΣ̓Α' COLLATE PG_UNICODE_FAST); -- 0391 0343 03A3 0343 0391
+ lower 
+-------
+ ἀσ̓α
+(1 row)
+
+SELECT lower('ᾼΣͅΑ' COLLATE PG_UNICODE_FAST); -- 0391 0345 03A3 0345 0391
+ lower 
+-------
+ ᾳσͅα
+(1 row)
+
+-- properties
+SELECT 'xyz' ~ '[[:alnum:]]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT 'xyz' !~ '[[:upper:]]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '@' !~ '[[:alnum:]]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '=' !~ '[[:punct:]]' COLLATE PG_UNICODE_FAST; -- symbols are not punctuation
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT 'a8a' ~ '[[:digit:]]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT '൧' ~ '\d' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+-- case mapping
+SELECT 'xYz' ~* 'XyZ' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT 'xAb' ~* '[W-Y]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT 'xAb' !~* '[c-d]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT 'Δ' ~* '[γ-λ]' COLLATE PG_UNICODE_FAST;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT 'δ' ~* '[Γ-Λ]' COLLATE PG_UNICODE_FAST; -- same as above with cases reversed
+ ?column? 
+----------
+ t
+(1 row)
+
diff --git a/src/test/regress/sql/collate.utf8.sql b/src/test/regress/sql/collate.utf8.sql
index 1f5f9ef491..c63928d38e 100644
--- a/src/test/regress/sql/collate.utf8.sql
+++ b/src/test/regress/sql/collate.utf8.sql
@@ -65,3 +65,63 @@ SELECT 'xAb' ~* '[W-Y]' COLLATE PG_C_UTF8;
 SELECT 'xAb' !~* '[c-d]' COLLATE PG_C_UTF8;
 SELECT 'Δ' ~* '[γ-λ]' COLLATE PG_C_UTF8;
 SELECT 'δ' ~* '[Γ-Λ]' COLLATE PG_C_UTF8; -- same as above with cases reversed
+
+--
+-- Test PG_UNICODE_FAST
+--
+
+CREATE COLLATION regress_pg_unicode_fast (
+  provider = builtin, locale = 'unicode'); -- fails
+CREATE COLLATION regress_pg_unicode_fast (
+  provider = builtin, locale = 'PG_UNICODE_FAST');
+
+CREATE TABLE test_pg_unicode_fast (
+  t TEXT COLLATE PG_UNICODE_FAST
+);
+INSERT INTO test_pg_unicode_fast VALUES
+  ('abc DEF 123abc'),
+  ('ábc sßs ßss DÉF'),
+  ('DŽxxDŽ džxxDž Džxxdž'),
+  ('ȺȺȺ'),
+  ('ⱥⱥⱥ'),
+  ('ⱥȺ');
+
+SELECT
+    t, lower(t), initcap(t), upper(t),
+    length(convert_to(t, 'UTF8')) AS t_bytes,
+    length(convert_to(lower(t), 'UTF8')) AS lower_t_bytes,
+    length(convert_to(initcap(t), 'UTF8')) AS initcap_t_bytes,
+    length(convert_to(upper(t), 'UTF8')) AS upper_t_bytes
+  FROM test_pg_unicode_fast;
+
+DROP TABLE test_pg_unicode_fast;
+
+-- test Final_Sigma
+SELECT lower('ΑΣ' COLLATE PG_UNICODE_FAST); -- 0391 03A3
+SELECT lower('ΑΣ0' COLLATE PG_UNICODE_FAST); -- 0391 03A3 0030
+SELECT lower('ἈΣ̓' COLLATE PG_UNICODE_FAST); -- 0391 0343 03A3 0343
+SELECT lower('ᾼΣͅ' COLLATE PG_UNICODE_FAST); -- 0391 0345 03A3 0345
+
+-- test !Final_Sigma
+SELECT lower('Σ' COLLATE PG_UNICODE_FAST); -- 03A3
+SELECT lower('0Σ' COLLATE PG_UNICODE_FAST); -- 0030 03A3
+SELECT lower('ΑΣΑ' COLLATE PG_UNICODE_FAST); -- 0391 03A3 0391
+SELECT lower('ἈΣ̓Α' COLLATE PG_UNICODE_FAST); -- 0391 0343 03A3 0343 0391
+SELECT lower('ᾼΣͅΑ' COLLATE PG_UNICODE_FAST); -- 0391 0345 03A3 0345 0391
+
+-- properties
+
+SELECT 'xyz' ~ '[[:alnum:]]' COLLATE PG_UNICODE_FAST;
+SELECT 'xyz' !~ '[[:upper:]]' COLLATE PG_UNICODE_FAST;
+SELECT '@' !~ '[[:alnum:]]' COLLATE PG_UNICODE_FAST;
+SELECT '=' !~ '[[:punct:]]' COLLATE PG_UNICODE_FAST; -- symbols are not punctuation
+SELECT 'a8a' ~ '[[:digit:]]' COLLATE PG_UNICODE_FAST;
+SELECT '൧' ~ '\d' COLLATE PG_UNICODE_FAST;
+
+-- case mapping
+
+SELECT 'xYz' ~* 'XyZ' COLLATE PG_UNICODE_FAST;
+SELECT 'xAb' ~* '[W-Y]' COLLATE PG_UNICODE_FAST;
+SELECT 'xAb' !~* '[c-d]' COLLATE PG_UNICODE_FAST;
+SELECT 'Δ' ~* '[γ-λ]' COLLATE PG_UNICODE_FAST;
+SELECT 'δ' ~* '[Γ-Λ]' COLLATE PG_UNICODE_FAST; -- same as above with cases reversed
-- 
2.34.1