MySQL Bugs: #33563: Backup: crash if restore in procedure

Bug #33563	Backup: crash if restore in procedure
Submitted:	28 Dec 2007 23:49	Modified:	14 Mar 2008 1:43
Reporter:	Peter Gulutzan	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Backup	Severity:	S3 (Non-critical)
Version:	6.0.5-alpha-debug	OS:	Linux (SUSE 10 64-bit)
Assigned to:	Rafal Somla	CPU Architecture:	Any

Description:
I create a procedure containing a RESTORE statement.
I call the procedure.
Crash.

Built from mysql-6.0-backup source with BUILD/compile-pentium-debug-max.
Last changeset = "ChangeSet@1.2753, 2007-12-20 15:32:22-05:00".

How to repeat:
mysql> create database x;
Query OK, 1 row affected (0.01 sec)

mysql> use x
Database changed

mysql> backup database x to '/usr/local/mysql/var/x3';
+-----------+
| backup_id |
+-----------+
| 7         |
+-----------+
1 row in set (1.68 sec)

mysql> restore from '/usr/local/mysql/var/x3';
+-----------+
| backup_id |
+-----------+
| 8         |
+-----------+
1 row in set (1.42 sec)

mysql> use x
Database changed
mysql> create procedure p () restore from '/usr/local/mysql/var/x3';
Query OK, 0 rows affected (0.01 sec)

mysql> call p();
ERROR 2013 (HY000): Lost connection to MySQL server during query

Thank you for the bug report. Verified as described:

mysql> create procedure p () restore from '/home/miguel/dbs/6.0b/x3';
Query OK, 0 rows affected (0.00 sec)

mysql> call p();
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql>

REFINED PROBLEM DESCRIPTION

Internally, RESTORE statement re-creates objects by executing CRATE ... statements, passing them to mysql_parse() function. This function is not intended to be called from inside stored routine. At the beginning it calls mysql_reset_thd_for_next_command(thd) which contains assertion  

DBUG_ASSERT(!thd->spcont)

This assertion fails and causes server to crash if mysql_parse() is executed from inside stored procedure.

Backup kernel is now being refactored to use object services (WL#3574 and WL#4205). When this happens, explicit execution of CREATE statements will be replaced by a call to service function which creates an object. This problem should be handled in the implementation of that function.

PROPOSED SOLUTION

It was decided (ask Lars) that in the first version BACKUP/RESTORE commands
will be disabled inside stored routines, triggers and events. We will work on enabling this functionality in later versions.

The bug will be fixed by disabling BACKUP/RESTORE statements inside stored routines. This should behave identical as for other statements which are not allowed there, that is error will be reported when stored procedure is created.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/41212

ChangeSet@1.2784, 2008-01-24 15:25:32+01:00, rafal@quant.(none) +3 -0
  Bug #33563  (Backup: crash if restore in procedure)
  
  This patch disables BACKUP/RESTORE statements inside stored routines thus avoiding 
  the crash.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/41307

ChangeSet@1.2784, 2008-01-28 15:01:12+01:00, rafal@quant.(none) +3 -0
  Bug #33563  (Backup: crash if restore in procedure)
  
  This patch disables BACKUP/RESTORE statements inside stored routines thus avoiding 
  the crash.

Patch approved.

Pushed into 6.0-backup tree.

Pushed into 6.0.5-alpha

No changelog entry needed; this bug did not appear in any released version.

Noted the restriction against BACKUP DATABASE or RESTORE appearing in stored programs in the restrictions appendix.