Bug#32948: FKs allowed to reference partitioned table

Problem: when alter to partitioned table,
it does not see it as change of engine.

Solution: If alter includes partitioning, check if it is possible
to change engines (eg. is the table referenced by a FK)

mysql-test/r/partition_innodb.result

+# Bug#32948
+CREATE TABLE t1 (c1 INT, PRIMARY KEY (c1)) ENGINE=INNODB;
+CREATE TABLE t2 (c1 INT, PRIMARY KEY (c1),
+FOREIGN KEY (c1) REFERENCES t1 (c1)
+ON DELETE CASCADE)
+ENGINE=INNODB;
+ALTER TABLE t1 PARTITION BY HASH(c1) PARTITIONS 5;
+ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails
+ALTER TABLE t1 ENGINE=MyISAM;
+ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails
+DROP TABLE t2;
+DROP TABLE t1;
 create table t1 (a int) engine=innodb partition by hash(a) ;
 show table status like 't1';
 Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment

mysql-test/t/partition_innodb.test

 --source include/have_partition.inc
 --source include/have_innodb.inc
 
+# Bug#32948 - FKs allowed to reference partitioned table
+#
+-- echo # Bug#32948
+CREATE TABLE t1 (c1 INT, PRIMARY KEY (c1)) ENGINE=INNODB;
+CREATE TABLE t2 (c1 INT, PRIMARY KEY (c1),
+                 FOREIGN KEY (c1) REFERENCES t1 (c1)
+                 ON DELETE CASCADE)
+ENGINE=INNODB;
+--error ER_ROW_IS_REFERENCED
+ALTER TABLE t1 PARTITION BY HASH(c1) PARTITIONS 5;
+--error ER_ROW_IS_REFERENCED
+ALTER TABLE t1 ENGINE=MyISAM;
+DROP TABLE t2;
+DROP TABLE t1;
+
 #
 # Bug #14673: Wrong InnoDB default row format
 #

sql/sql_table.cc

@@ -5974,7 +5974,8 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
     goto err;
   new_db_type= create_info->db_type;
 
-  if (new_db_type != old_db_type &&
+  if ((new_db_type != old_db_type ||
+       alter_info->flags & ALTER_PARTITION) &&
       !table->file->can_switch_engines())
   {
     my_error(ER_ROW_IS_REFERENCED, MYF(0));