Handle new option colliculocale in CREATE COLLATION logic

In PG15, there is an added option to use ICU as global locale provider.
pg_collation has three locale-related fields: collcollate and collctype,
which are libc-related fields, and a new one colliculocale, which is the
ICU-related field. Only the libc-related fields or the ICU-related field
is set, never both.

Relevant PG commits:
f2553d43060edb210b36c63187d52a632448e1d2
54637508f87bd5f07fb9406bac6b08240283be3b

src/backend/distributed/commands/collation.c

@@ -63,15 +63,53 @@ CreateCollationDDLInternal(Oid collationId, Oid *collowner, char **quotedCollati
 	const char *collname = NameStr(collationForm->collname);
 	bool collisdeterministic = collationForm->collisdeterministic;
 
+	char *collcollate;
+	char *collctype;
+
 #if PG_VERSION_NUM >= PG_VERSION_15
+
+	/*
+	 * In PG15, there is an added option to use ICU as global locale provider.
+	 * pg_collation has three locale-related fields: collcollate and collctype,
+	 * which are libc-related fields, and a new one colliculocale, which is the
+	 * ICU-related field. Only the libc-related fields or the ICU-related field
+	 * is set, never both.
+	 */
+	char *colliculocale;
 	bool isnull;
+
 	Datum datum = SysCacheGetAttr(COLLOID, heapTuple, Anum_pg_collation_collcollate,
 								  &isnull);
-	Assert(!isnull);
+	if (!isnull)
-	char *collcollate = TextDatumGetCString(datum);
+	{
+		collcollate = TextDatumGetCString(datum);
+	}
+	else
+	{
+		collcollate = NULL;
+	}
+
 	datum = SysCacheGetAttr(COLLOID, heapTuple, Anum_pg_collation_collctype, &isnull);
-	Assert(!isnull);
+	if (!isnull)
-	char *collctype = TextDatumGetCString(datum);
+	{
+		collctype = TextDatumGetCString(datum);
+	}
+	else
+	{
+		collctype = NULL;
+	}
+
+	datum = SysCacheGetAttr(COLLOID, heapTuple, Anum_pg_collation_colliculocale, &isnull);
+	if (!isnull)
+	{
+		colliculocale = TextDatumGetCString(datum);
+	}
+	else
+	{
+		colliculocale = NULL;
+	}
+
+	AssertArg((collcollate && collctype) || colliculocale);
 #else
 
 	/*
@@ -79,8 +117,8 @@ CreateCollationDDLInternal(Oid collationId, Oid *collowner, char **quotedCollati
 	 * pstrdup() to match the interface of 15 so that we consistently free the
 	 * result later.
 	 */
-	char *collcollate = pstrdup(NameStr(collationForm->collcollate));
+	collcollate = pstrdup(NameStr(collationForm->collcollate));
-	char *collctype = pstrdup(NameStr(collationForm->collctype));
+	collctype = pstrdup(NameStr(collationForm->collctype));
 #endif
 
 	if (collowner != NULL)
@@ -106,6 +144,33 @@ CreateCollationDDLInternal(Oid collationId, Oid *collowner, char **quotedCollati
 					 "CREATE COLLATION %s (provider = '%s'",
 					 *quotedCollationName, providerString);
 
+#if PG_VERSION_NUM >= PG_VERSION_15
+	if (colliculocale)
+	{
+		appendStringInfo(&collationNameDef,
+						 ", locale = %s",
+						 quote_literal_cstr(colliculocale));
+		pfree(colliculocale);
+	}
+	else
+	{
+		if (strcmp(collcollate, collctype) == 0)
+		{
+			appendStringInfo(&collationNameDef,
+							 ", locale = %s",
+							 quote_literal_cstr(collcollate));
+		}
+		else
+		{
+			appendStringInfo(&collationNameDef,
+							 ", lc_collate = %s, lc_ctype = %s",
+							 quote_literal_cstr(collcollate),
+							 quote_literal_cstr(collctype));
+		}
+		pfree(collcollate);
+		pfree(collctype);
+	}
+#else
 	if (strcmp(collcollate, collctype) == 0)
 	{
 		appendStringInfo(&collationNameDef,
@@ -122,6 +187,7 @@ CreateCollationDDLInternal(Oid collationId, Oid *collowner, char **quotedCollati
 
 	pfree(collcollate);
 	pfree(collctype);
+#endif
 
 	if (!collisdeterministic)
 	{

src/test/regress/expected/pg15.out

@@ -0,0 +1,100 @@
+--
+-- PG15
+--
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+\else
+\q
+\endif
+CREATE SCHEMA pg15;
+SET search_path TO pg15;
+SET citus.next_shard_id TO 960000;
+SET citus.shard_count TO 4;
+--
+-- In PG15, there is an added option to use ICU as global locale provider.
+-- pg_collation has three locale-related fields: collcollate and collctype,
+-- which are libc-related fields, and a new one colliculocale, which is the
+-- ICU-related field. Only the libc-related fields or the ICU-related field
+-- is set, never both.
+-- Relevant PG commits:
+-- f2553d43060edb210b36c63187d52a632448e1d2
+-- 54637508f87bd5f07fb9406bac6b08240283be3b
+--
+-- fail, needs "locale"
+CREATE COLLATION german_phonebook_test (provider = icu, lc_collate = 'de-u-co-phonebk');
+ERROR:  parameter "locale" must be specified
+-- fail, needs "locale"
+CREATE COLLATION german_phonebook_test (provider = icu, lc_collate = 'de-u-co-phonebk', lc_ctype = 'de-u-co-phonebk');
+ERROR:  parameter "locale" must be specified
+-- works
+CREATE COLLATION german_phonebook_test (provider = icu, locale = 'de-u-co-phonebk');
+-- with icu provider, colliculocale will be set, collcollate and collctype will be null
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collcollate FROM pg_collation WHERE collname = ''german_phonebook_test'';
+');
+ result
+---------------------------------------------------------------------
+
+
+
+(3 rows)
+
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collctype FROM pg_collation WHERE collname = ''german_phonebook_test'';
+');
+ result
+---------------------------------------------------------------------
+
+
+
+(3 rows)
+
+SELECT result FROM run_command_on_all_nodes('
+    SELECT colliculocale FROM pg_collation WHERE collname = ''german_phonebook_test'';
+');
+     result
+---------------------------------------------------------------------
+ de-u-co-phonebk
+ de-u-co-phonebk
+ de-u-co-phonebk
+(3 rows)
+
+-- with non-icu provider, colliculocale will be null, collcollate and collctype will be set
+CREATE COLLATION default_provider (provider = libc, lc_collate = "POSIX", lc_ctype = "POSIX");
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collcollate FROM pg_collation WHERE collname = ''default_provider'';
+');
+ result
+---------------------------------------------------------------------
+ POSIX
+ POSIX
+ POSIX
+(3 rows)
+
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collctype FROM pg_collation WHERE collname = ''default_provider'';
+');
+ result
+---------------------------------------------------------------------
+ POSIX
+ POSIX
+ POSIX
+(3 rows)
+
+SELECT result FROM run_command_on_all_nodes('
+    SELECT colliculocale FROM pg_collation WHERE collname = ''default_provider'';
+');
+ result
+---------------------------------------------------------------------
+
+
+
+(3 rows)
+
+-- Clean up
+DROP SCHEMA pg15 CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to collation german_phonebook_test
+drop cascades to collation default_provider

src/test/regress/expected/pg15_0.out

@@ -0,0 +1,9 @@
+--
+-- PG15
+--
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+\else
+\q

src/test/regress/multi_schedule

@@ -58,6 +58,7 @@ test: cte_inline recursive_view_local_table values sequences_with_different_type
 test: pg13 pg12
 # run pg14 sequentially as it syncs metadata
 test: pg14
+test: pg15
 test: drop_column_partitioned_table
 test: tableam
 

src/test/regress/sql/pg15.sql

@@ -0,0 +1,62 @@
+--
+-- PG15
+--
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+\else
+\q
+\endif
+
+CREATE SCHEMA pg15;
+SET search_path TO pg15;
+SET citus.next_shard_id TO 960000;
+SET citus.shard_count TO 4;
+
+--
+-- In PG15, there is an added option to use ICU as global locale provider.
+-- pg_collation has three locale-related fields: collcollate and collctype,
+-- which are libc-related fields, and a new one colliculocale, which is the
+-- ICU-related field. Only the libc-related fields or the ICU-related field
+-- is set, never both.
+-- Relevant PG commits:
+-- f2553d43060edb210b36c63187d52a632448e1d2
+-- 54637508f87bd5f07fb9406bac6b08240283be3b
+--
+
+-- fail, needs "locale"
+CREATE COLLATION german_phonebook_test (provider = icu, lc_collate = 'de-u-co-phonebk');
+
+-- fail, needs "locale"
+CREATE COLLATION german_phonebook_test (provider = icu, lc_collate = 'de-u-co-phonebk', lc_ctype = 'de-u-co-phonebk');
+
+-- works
+CREATE COLLATION german_phonebook_test (provider = icu, locale = 'de-u-co-phonebk');
+
+-- with icu provider, colliculocale will be set, collcollate and collctype will be null
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collcollate FROM pg_collation WHERE collname = ''german_phonebook_test'';
+');
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collctype FROM pg_collation WHERE collname = ''german_phonebook_test'';
+');
+SELECT result FROM run_command_on_all_nodes('
+    SELECT colliculocale FROM pg_collation WHERE collname = ''german_phonebook_test'';
+');
+
+-- with non-icu provider, colliculocale will be null, collcollate and collctype will be set
+CREATE COLLATION default_provider (provider = libc, lc_collate = "POSIX", lc_ctype = "POSIX");
+
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collcollate FROM pg_collation WHERE collname = ''default_provider'';
+');
+SELECT result FROM run_command_on_all_nodes('
+    SELECT collctype FROM pg_collation WHERE collname = ''default_provider'';
+');
+SELECT result FROM run_command_on_all_nodes('
+    SELECT colliculocale FROM pg_collation WHERE collname = ''default_provider'';
+');
+
+-- Clean up
+DROP SCHEMA pg15 CASCADE;