v7-0003-Handle-the-und-locale-in-ICU-versions-54-and-olde.patch

From 8027572146571609927815d0fe14f761fc86cf2c Mon Sep 17 00:00:00 2001
From: Jeff Davis <jeff@j-davis.com>
Date: Tue, 14 Mar 2023 22:28:21 -0700
Subject: [PATCH v7 3/7] Handle the "und" locale in ICU versions 54 and older.

The "und" locale is an alternative spelling of the root locale, but it
was not recognized until ICU 55. To maintain common behavior across
all supported ICU versions, check for "und" and replace with "root"
before opening.

Previously, the lack of support for "und" was dangerous, because
versions 54 and older fall back to the environment when a locale is
not found. If the user specified "und" for the language (which is
expected and documented), it could not only resolve to the wrong
collator, but it could unexpectedly change (which could lead to
corrupt indexes).

This effectively reverts commit d72900bded, which worked around the
problem for the built-in "unicode" collation, and is no longer
necessary.

Discussion: https://postgr.es/m/60da0cecfb512a78b8666b31631a636215d8ce73.camel@j-davis.com
Discussion: https://postgr.es/m/0c6fa66f2753217d2a40480a96bd2ccf023536a1.camel@j-davis.com
---
 src/backend/utils/adt/pg_locale.c             | 38 ++++++++++++++++++-
 src/bin/initdb/initdb.c                       |  2 +-
 .../regress/expected/collate.icu.utf8.out     |  7 ++++
 src/test/regress/sql/collate.icu.utf8.sql     |  2 +
 4 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index dd0786dff5..052db11413 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -2501,8 +2501,9 @@ pg_strnxfrm_prefix(char *dest, size_t destsize, const char *src,
 static UCollator *
 pg_ucol_open(const char *loc_str)
 {
-	UCollator  *collator;
-	UErrorCode	status;
+	UCollator	*collator;
+	UErrorCode	 status;
+	char		*fixed_str = NULL;
 
 	/*
 	 * Must never open default collator, because it depends on the environment
@@ -2517,6 +2518,36 @@ pg_ucol_open(const char *loc_str)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("opening default collator is not supported")));
 
+	/*
+	 * In ICU versions 54 and earlier, "und" is not a recognized spelling of
+	 * the root locale. If the first component of the locale is "und", replace
+	 * with "root" before opening.
+	 */
+	if (U_ICU_VERSION_MAJOR_NUM < 55)
+	{
+		char  lang[ULOC_LANG_CAPACITY];
+
+		status = U_ZERO_ERROR;
+		uloc_getLanguage(loc_str, lang, ULOC_LANG_CAPACITY, &status);
+		if (U_FAILURE(status))
+		{
+			ereport(ERROR,
+					(errmsg("could not get language from locale \"%s\": %s",
+							loc_str, u_errorName(status))));
+		}
+
+		if (strcmp(lang, "und") == 0)
+		{
+			const char *remainder = loc_str + strlen("und");
+
+			fixed_str = palloc(strlen("root") + strlen(remainder) + 1);
+			strcpy(fixed_str, "root");
+			strcat(fixed_str, remainder);
+
+			loc_str = fixed_str;
+		}
+	}
+
 	status = U_ZERO_ERROR;
 	collator = ucol_open(loc_str, &status);
 	if (U_FAILURE(status))
@@ -2527,6 +2558,9 @@ pg_ucol_open(const char *loc_str)
 	if (U_ICU_VERSION_MAJOR_NUM < 54)
 		icu_set_collation_attributes(collator, loc_str);
 
+	if (fixed_str != NULL)
+		pfree(fixed_str);
+
 	return collator;
 }
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 68d430ed63..d48b7b6060 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1498,7 +1498,7 @@ setup_collation(FILE *cmdfd)
 	 * 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, '');\n\n",
+				  "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)"
diff --git a/src/test/regress/expected/collate.icu.utf8.out b/src/test/regress/expected/collate.icu.utf8.out
index 6225b575ce..f135200c99 100644
--- a/src/test/regress/expected/collate.icu.utf8.out
+++ b/src/test/regress/expected/collate.icu.utf8.out
@@ -1312,6 +1312,13 @@ SELECT 'aBcD' COLLATE lt_insensitive = 'AbCd' COLLATE lt_insensitive;
  t
 (1 row)
 
+CREATE COLLATION lt_upperfirst (provider = icu, locale = 'und-u-kf-upper');
+SELECT 'Z' COLLATE lt_upperfirst < 'z' COLLATE lt_upperfirst;
+ ?column? 
+----------
+ t
+(1 row)
+
 CREATE TABLE test1cs (x text COLLATE case_sensitive);
 CREATE TABLE test2cs (x text COLLATE case_sensitive);
 CREATE TABLE test3cs (x text COLLATE case_sensitive);
diff --git a/src/test/regress/sql/collate.icu.utf8.sql b/src/test/regress/sql/collate.icu.utf8.sql
index 64cbfd0a5b..8105ebc8ae 100644
--- a/src/test/regress/sql/collate.icu.utf8.sql
+++ b/src/test/regress/sql/collate.icu.utf8.sql
@@ -521,6 +521,8 @@ SELECT 'abc' <= 'ABC' COLLATE case_insensitive, 'abc' >= 'ABC' COLLATE case_inse
 -- test language tags
 CREATE COLLATION lt_insensitive (provider = icu, locale = 'en-u-ks-level1', deterministic = false);
 SELECT 'aBcD' COLLATE lt_insensitive = 'AbCd' COLLATE lt_insensitive;
+CREATE COLLATION lt_upperfirst (provider = icu, locale = 'und-u-kf-upper');
+SELECT 'Z' COLLATE lt_upperfirst < 'z' COLLATE lt_upperfirst;
 
 CREATE TABLE test1cs (x text COLLATE case_sensitive);
 CREATE TABLE test2cs (x text COLLATE case_sensitive);
-- 
2.34.1