MySQL Bugs: #30648: Partition handler may not initialize variable used w/ autoincrement

Bug #30648	Partition handler may not initialize variable used w/ autoincrement
Submitted:	27 Aug 2007 17:47	Modified:	31 Aug 2007 13:48
Reporter:	Timothy Smith	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Partitions	Severity:	S3 (Non-critical)
Version:	5.1	OS:	Any
Assigned to:	Timothy Smith	CPU Architecture:	Any

Description:
Quick bug filed for problem found by partition_innodb.test, where the following would fail:

create table t1 (a int auto_increment primary key) engine = innodb partition by key (a);

insert into t1 values (NULL), (NULL), (NULL), (NULL);

Fails with:

mysqltest: At line 26: query 'insert into t1 values (NULL), (NULL), (NULL), (NULL)' failed: 1022: Can't write; duplicate key in table 't1'

How to repeat:
With new InnoDB autoincrement fixes, run the above statements.

Suggested fix:
Initialize first_value_part in ha_partition::get_auto_increment() with *first_value before it's used in the underlying table handler.  Thanks to Antony for digging up this fix.

--- 1.98/sql/ha_partition.cc    2007-07-04 21:55:21 +02:00
+++ 1.99/sql/ha_partition.cc    2007-07-20 01:52:41 +02:00
@@ -5432,6 +5432,7 @@ void ha_partition::get_auto_increment(ul

   for (pos=m_file, end= m_file+ m_tot_parts; pos != end ; pos++)
   {
+    first_value_part= *first_value;
     (*pos)->get_auto_increment(offset, increment, nb_desired_values,
                                &first_value_part, &nb_reserved_values_part);
     if (first_value_part == ~(ulonglong)(0)) // error in one partition

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/33164

ChangeSet@1.2576, 2007-08-27 11:46:34-06:00, tsmith@ramayana.hindu.god +1 -0
  Bug #30648: Partition handler may not initialize variable used w/ autoincrement
  
  A local variable may be used uninitialized in 
  ha_partition::get_auto_increment().  Initialize it properly.

Patch has been pushed to 5.1.22 tree.

Queued to target-5.1.22

Docs team: I'm not aware of any release in which this bug would show up.  It became visible only after some changes to InnoDB's auto-increment handling (see bug #16979), but I don't have a test case against any released version of MySQL which tickles this bug.

So, it may not need to be documented.  The symptom, by the way, was that partitioning an innodb table based on an auto_increment key failed to generate correct values for the key column.  Instead, it would use the contents of some uninitialized variable, repeatedly (i.e., you get the same junk value over and over).

No changelog entry needed.

Pushed into 5.1.23-beta