From a8e33d010f60cceb9442123bd0531451875df313 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 9 Mar 2023 11:14:28 +0100
Subject: [PATCH v2] Add standard collation UNICODE

Discussion: https://www.postgresql.org/message-id/flat/1293e382-2093-a2bf-a397-c04e8f83d3c2@enterprisedb.com
---
 doc/src/sgml/charset.sgml | 31 ++++++++++++++++++++++++++++---
 src/bin/initdb/initdb.c   | 10 +++++++---
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/doc/src/sgml/charset.sgml b/doc/src/sgml/charset.sgml
index 3032392b80..12fabb7372 100644
--- a/doc/src/sgml/charset.sgml
+++ b/doc/src/sgml/charset.sgml
@@ -659,9 +659,34 @@ <title>Standard Collations</title>
    </para>
 
    <para>
-    Additionally, the SQL standard collation name <literal>ucs_basic</literal>
-    is available for encoding <literal>UTF8</literal>.  It is equivalent
-    to <literal>C</literal> and sorts by Unicode code point.
+    Additionally, two SQL standard collation names are available:
+
+    <variablelist>
+     <varlistentry>
+      <term><literal>unicode</literal></term>
+      <listitem>
+       <para>
+        This collation sorts using the Unicode Collation Algorithm with the
+        Default Unicode Collation Element Table.  It is available in all
+        encodings.  ICU support is required to use this collation.  (This
+        collation has the same behavior as the ICU root locale; see <xref
+        linkend="collation-managing-predefined-icu-und-x-icu"/>.)
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><literal>ucs_basic</literal></term>
+      <listitem>
+       <para>
+        This collation sorts by Unicode code point.  It is only available for
+        encoding <literal>UTF8</literal>.  (This collation has the same
+        behavior as the libc locale specification <literal>C</literal> in
+        <literal>UTF8</literal> encoding.)
+       </para>
+      </listitem>
+     </varlistentry>
+    </variablelist>
    </para>
   </sect3>
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 5e3c6a27c4..d303cc5609 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1486,10 +1486,14 @@ static void
 setup_collation(FILE *cmdfd)
 {
 	/*
-	 * Add an SQL-standard name.  We don't want to pin this, so it doesn't go
-	 * in pg_collation.h.  But add it before reading system collations, so
-	 * that it wins if libc defines a locale named ucs_basic.
+	 * Add SQL-standard names.  We don't want to pin these, so they don't go
+	 * in pg_collation.dat.  But add them before reading system collations, so
+	 * that they win if libc defines a locale with the same name.
 	 */
+	PG_CMD_PRINTF("INSERT INTO pg_collation (oid, collname, collnamespace, collowner, collprovider, collisdeterministic, collencoding, colliculocale)"
+				  "VALUES (pg_nextoid('pg_catalog.pg_collation', 'oid', 'pg_catalog.pg_collation_oid_index'), 'unicode', 'pg_catalog'::regnamespace, %u, '%c', true, -1, 'und');\n\n",
+				  BOOTSTRAP_SUPERUSERID, COLLPROVIDER_ICU);
+
 	PG_CMD_PRINTF("INSERT INTO pg_collation (oid, collname, collnamespace, collowner, collprovider, collisdeterministic, collencoding, collcollate, collctype)"
 				  "VALUES (pg_nextoid('pg_catalog.pg_collation', 'oid', 'pg_catalog.pg_collation_oid_index'), 'ucs_basic', 'pg_catalog'::regnamespace, %u, '%c', true, %d, 'C', 'C');\n\n",
 				  BOOTSTRAP_SUPERUSERID, COLLPROVIDER_LIBC, PG_UTF8);

base-commit: 36ea345f8fa616fd9b40576310e54145aa70c1a1
-- 
2.39.2