MDEV-18923 Assertion `!lex_string_cmp(system_charset_info,...

MDEV-18923 Assertion `!lex_string_cmp(system_charset_info, fk_info->referenced_table, &table->s->table_name)' failed in fk_truncate_illegal_if_parent

don't assert the correctness of FK constraints, as it can be
broken under `SET FOREIGN_KEY_CHECKS= OFF`

mysql-test/suite/innodb/r/innodb-truncate.result

@@ -66,3 +66,16 @@ a
 1
 2
 DROP TABLE t1;
+call mtr.add_suppression('InnoDB: Error: in RENAME TABLE table `test`.`t3`');
+SET FOREIGN_KEY_CHECKS= OFF;
+CREATE TABLE t1 (f2 INT, f4 INT, KEY(f2), FOREIGN KEY (f4) REFERENCES t3 (f4)) ENGINE=InnoDB;
+SET FOREIGN_KEY_CHECKS= ON;
+CREATE TABLE t2 (f2 INT, FOREIGN KEY(f2) REFERENCES t1 (f2)) ENGINE=InnoDB;
+CREATE TABLE t3 (a INT) ENGINE=InnoDB;
+ERROR HY000: Can't create table 'test.t3' (errno: 150)
+ALTER TABLE t1 RENAME TO t3;
+ERROR HY000: Error on rename of './test/t1' to './test/t3' (errno: 150)
+ALTER TABLE t1 FORCE;
+TRUNCATE TABLE t1;
+ERROR 42000: Cannot truncate a table referenced in a foreign key constraint (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`f2`) REFERENCES `test`.`t3` (`f2`))
+DROP TABLE t2, t1;

mysql-test/suite/innodb/t/innodb-truncate.test

@@ -62,3 +62,19 @@ INSERT INTO t1 VALUES (NULL), (NULL);
 SELECT * FROM t1 ORDER BY a;
 DROP TABLE t1;
 
+#
+# MDEV-18923 Assertion `!lex_string_cmp(system_charset_info, fk_info->referenced_table, &table->s->table_name)' failed in fk_truncate_illegal_if_parent
+#
+call mtr.add_suppression('InnoDB: Error: in RENAME TABLE table `test`.`t3`');
+SET FOREIGN_KEY_CHECKS= OFF;
+CREATE TABLE t1 (f2 INT, f4 INT, KEY(f2), FOREIGN KEY (f4) REFERENCES t3 (f4)) ENGINE=InnoDB;
+SET FOREIGN_KEY_CHECKS= ON;
+CREATE TABLE t2 (f2 INT, FOREIGN KEY(f2) REFERENCES t1 (f2)) ENGINE=InnoDB;
+--error ER_CANT_CREATE_TABLE
+CREATE TABLE t3 (a INT) ENGINE=InnoDB;
+--error ER_ERROR_ON_RENAME
+ALTER TABLE t1 RENAME TO t3;
+ALTER TABLE t1 FORCE;
+--error ER_TRUNCATE_ILLEGAL_FK
+TRUNCATE TABLE t1;
+DROP TABLE t2, t1;

sql/sql_truncate.cc

@@ -150,15 +150,11 @@ fk_truncate_illegal_if_parent(THD *thd, TABLE *table)
   /* Loop over the set of foreign keys for which this table is a parent. */
   while ((fk_info= it++))
   {
-    DBUG_ASSERT(!my_strcasecmp(system_charset_info,
-                               fk_info->referenced_db->str,
-                               table->s->db.str));
-
-    DBUG_ASSERT(!my_strcasecmp(system_charset_info,
-                               fk_info->referenced_table->str,
-                               table->s->table_name.str));
-
-    if (my_strcasecmp(system_charset_info, fk_info->foreign_db->str,
+    if (my_strcasecmp(system_charset_info, fk_info->referenced_db->str,
+                      table->s->db.str) ||
+        my_strcasecmp(system_charset_info, fk_info->referenced_table->str,
+                      table->s->table_name.str) ||
+        my_strcasecmp(system_charset_info, fk_info->foreign_db->str,
                       table->s->db.str) ||
         my_strcasecmp(system_charset_info, fk_info->foreign_table->str,
                       table->s->table_name.str))