When creating a collation, check that the locales can be loaded

This is the same check that would happen later when the collation is
used, but it's friendlier to check the collation already when it is
created.

src/backend/commands/collationcmds.c

@@ -15,6 +15,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/xact.h"
 #include "catalog/dependency.h"
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
@@ -30,6 +31,7 @@
 #include "utils/acl.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
+#include "utils/pg_locale.h"
 #include "utils/syscache.h"
 
 static void AlterCollationOwner_internal(Relation rel, Oid collationOid,
@@ -51,6 +53,7 @@ DefineCollation(List *names, List *parameters)
 	DefElem	   *lcctypeEl = NULL;
 	char	   *collcollate = NULL;
 	char	   *collctype = NULL;
+	Oid			newoid;
 
 	collNamespace = QualifiedNameGetCreationNamespace(names, &collName);
 
@@ -130,12 +133,16 @@ DefineCollation(List *names, List *parameters)
 
 	check_encoding_locale_matches(GetDatabaseEncoding(), collcollate, collctype);
 
-	CollationCreate(collName,
+	newoid = CollationCreate(collName,
 					collNamespace,
 					GetUserId(),
 					GetDatabaseEncoding(),
 					collcollate,
 					collctype);
+
+	/* check that the locales can be loaded */
+	CommandCounterIncrement();
+	pg_newlocale_from_collation(newoid);
 }
 
 /*

src/test/regress/expected/collate.linux.utf8.out

@@ -744,6 +744,8 @@ ERROR:  encoding UTF8 does not match locale en_US
 DETAIL:  The chosen LC_CTYPE setting requires encoding LATIN1.
 CREATE COLLATION test3 (lc_collate = 'en_US.utf8'); -- fail
 ERROR:  parameter "lc_ctype" must be specified
+CREATE COLLATION testx (locale = 'nonsense'); -- fail
+ERROR:  could not create locale "nonsense": No such file or directory
 CREATE COLLATION test4 FROM nonsense;
 ERROR:  collation "nonsense" for current database encoding "UTF8" does not exist
 CREATE COLLATION test5 FROM test0;

src/test/regress/sql/collate.linux.utf8.sql

@@ -234,6 +234,7 @@ CREATE COLLATION test0 (locale = 'en_US.utf8'); -- fail
 CREATE COLLATION test1 (lc_collate = 'en_US.utf8', lc_ctype = 'de_DE.utf8');
 CREATE COLLATION test2 (locale = 'en_US'); -- fail
 CREATE COLLATION test3 (lc_collate = 'en_US.utf8'); -- fail
+CREATE COLLATION testx (locale = 'nonsense'); -- fail
 
 CREATE COLLATION test4 FROM nonsense;
 CREATE COLLATION test5 FROM test0;