MDEV-26518 ; Galera incorrectly handles primary or unique keys with any multi-byte character set

We need to set temporary buffer large enough to fit also multi-byte
characters.

mysql-test/suite/galera/r/galera_fk_multibyte.result

@@ -0,0 +1,33 @@
+create table p (i varchar(100) primary key, j int) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+create table c1 (i int primary key auto_increment, j varchar(100), k int,  key(j), constraint fk1 foreign key (j) references p(i)) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+create table c2 (i int primary key auto_increment, j varchar(100), k int,  key(j), constraint fk2 foreign key (j) references p(i)) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+insert into p values('sippo',1);
+insert into c1 values(1,'sippo',1);
+insert into c2 values(1,'sippo',1);
+update c1 set k = 100 where j = 'sippo';
+insert into c1 values(2,'sippo',1);
+select * from p;
+i	j
+sippo	1
+select * from c1;
+i	j	k
+1	sippo	100
+2	sippo	1
+select * from c2;
+i	j	k
+1	sippo	1
+connection node_2;
+select * from p;
+i	j
+sippo	1
+select * from c1;
+i	j	k
+1	sippo	100
+2	sippo	1
+select * from c2;
+i	j	k
+1	sippo	1
+connection node_1;
+drop table c1;
+drop table c2;
+drop table p;

mysql-test/suite/galera/r/galera_fulltext.result

@@ -62,3 +62,31 @@ COUNT(*)
 1
 connection node_1;
 DROP TABLE t;
+connection node_1;
+SET @value=REPEAT (1,5001);
+CREATE TABLE t (a VARCHAR(5000),FULLTEXT (a)) engine=innodb DEFAULT CHARSET=utf8;
+INSERT IGNORE INTO t VALUES(@value);
+Warnings:
+Warning	1265	Data truncated for column 'a' at row 1
+SELECT COUNT(*) FROM t;
+COUNT(*)
+1
+connection node_2;
+SELECT COUNT(*) FROM t;
+COUNT(*)
+1
+connection node_1;
+DROP TABLE t;
+CREATE TABLE t (a VARCHAR(5000)) engine=innodb DEFAULT CHARSET=utf8;
+INSERT IGNORE INTO t VALUES(@value);
+Warnings:
+Warning	1265	Data truncated for column 'a' at row 1
+SELECT COUNT(*) FROM t;
+COUNT(*)
+1
+connection node_2;
+SELECT COUNT(*) FROM t;
+COUNT(*)
+1
+connection node_1;
+DROP TABLE t;

mysql-test/suite/galera/t/galera_fk_multibyte.test

@@ -0,0 +1,23 @@
+--source include/galera_cluster.inc
+
+create table p (i varchar(100) primary key, j int) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+create table c1 (i int primary key auto_increment, j varchar(100), k int,  key(j), constraint fk1 foreign key (j) references p(i)) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+create table c2 (i int primary key auto_increment, j varchar(100), k int,  key(j), constraint fk2 foreign key (j) references p(i)) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+insert into p values('sippo',1);
+insert into c1 values(1,'sippo',1);
+insert into c2 values(1,'sippo',1);
+update c1 set k = 100 where j = 'sippo';
+insert into c1 values(2,'sippo',1);
+select * from p;
+select * from c1;
+select * from c2;
+
+--connection node_2
+select * from p;
+select * from c1;
+select * from c2;
+
+--connection node_1
+drop table c1;
+drop table c2;
+drop table p;

mysql-test/suite/galera/t/galera_fulltext.test

@@ -83,3 +83,27 @@ SELECT COUNT(*) FROM t;
 
 --connection node_1
 DROP TABLE t;
+
+#
+# Case 2: UTF-8
+#
+--connection node_1
+SET @value=REPEAT (1,5001);
+CREATE TABLE t (a VARCHAR(5000),FULLTEXT (a)) engine=innodb DEFAULT CHARSET=utf8;
+INSERT IGNORE INTO t VALUES(@value);
+SELECT COUNT(*) FROM t;
+
+--connection node_2
+SELECT COUNT(*) FROM t;
+
+--connection node_1
+DROP TABLE t;
+CREATE TABLE t (a VARCHAR(5000)) engine=innodb DEFAULT CHARSET=utf8;
+INSERT IGNORE INTO t VALUES(@value);
+SELECT COUNT(*) FROM t;
+
+--connection node_2
+SELECT COUNT(*) FROM t;
+
+--connection node_1
+DROP TABLE t;

storage/innobase/handler/ha_innodb.cc

@@ -6750,7 +6750,8 @@ wsrep_innobase_mysql_sort(
 
 		// Note that strnxfrm may change length of string
 		tmp_length= charset->coll->strnxfrmlen(charset, str_length);
-		tmp_length= ut_max(str_length, tmp_length) + 1;
+		tmp_length= tmp_length * charset->mbmaxlen;
+		tmp_length= ut_max(str_length, tmp_length) + charset->mbmaxlen;
 		tmp_str= static_cast<uchar *>(ut_malloc_nokey(tmp_length));
 		ut_ad(str_length <= tmp_length);
 		memcpy(tmp_str, str, str_length);