TiDB-Server panic when creating views with SELECT ... INTO syntax

[bb7133]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

tidb> create view v1 as select 5 into outfile 'ttt';

2. What did you expect to see?
   In MySQL:

mysql> create view v1 as select 5 into outfile 'ttt';
ERROR 1350 (HY000): View's SELECT contains a 'INTO' clause

3. What did you see instead?
   TiDB Server got panic with following errros:

panic:interface conversion: *core.SelectInto is not core.LogicalPlan: missing method BuildKeyInfo -- create view v1 as select 5 into outfile 'ttt'

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?
   The latest master.