InnoDB: Prevent ALTER TABLE ... ENGINE=...

if there are foreign key constraints on the table. (Bug #5574)


sql/ha_innodb.cc:
  Add method can_switch_engines()
sql/ha_innodb.h:
  Add method can_switch_engines()
sql/handler.h:
  Add method can_switch_engines()
sql/sql_table.cc:
  Check handler::can_switch_engines() before switching storage engines

1 files changed, 26 insertions, 0 deletions

diff --git a/sql/ha_innodb.cc b/sql/ha_innodb.cc
index 3e3a48f4ab9..322d5188a75 100644
--- a/sql/ha_innodb.cc
+++ b/sql/ha_innodb.cc
@@ -4789,6 +4789,32 @@ ha_innobase::get_foreign_key_create_info(void)
   	return(str);
 }
 
+/*********************************************************************
+Checks if ALTER TABLE may change the storage engine of the table.
+Changing storage engines is not allowed for tables for which there
+are foreign key constraints (parent or child tables). */
+
+bool
+ha_innobase::can_switch_engines(void)
+/*=================================*/
+{
+	row_prebuilt_t* prebuilt	= (row_prebuilt_t*) innobase_prebuilt;
+	bool	can_switch;
+
+ 	DBUG_ENTER("ha_innobase::can_switch_engines");
+	prebuilt->trx->op_info =
+			"determining if there are foreign key constraints";
+	row_mysql_lock_data_dictionary(prebuilt->trx);
+
+	can_switch = !UT_LIST_GET_FIRST(prebuilt->table->referenced_list)
+			&& !UT_LIST_GET_FIRST(prebuilt->table->foreign_list);
+
+	row_mysql_unlock_data_dictionary(prebuilt->trx);
+	prebuilt->trx->op_info = "";
+
+	DBUG_RETURN(can_switch);
+}
+
 /***********************************************************************
 Checks if a table is referenced by a foreign key. The MySQL manual states that
 a REPLACE is either equivalent to an INSERT, or DELETE(s) + INSERT. Only a