Bug #27855 5.1 log table crashes 5.0
Submitted: 16 Apr 2007 17:05 Modified: 18 Apr 2007 16:22
Reporter: Andrey Hristov Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: CSV Severity:S2 (Serious)
Version:5.1 OS:Any
Assigned to: CPU Architecture:Any

[16 Apr 2007 17:05] Andrey Hristov
Description:
1. Enable logging to tables in 5.1 with:
   set global general_log=1;
2. Issue SELECT 1;
3. Stop the server
4. Start 5.0 server
5. Run SELECT * from mysql.general_log 

mysql> truncate mysql.general_log;
Query OK, 0 rows affected (0.05 sec)

mysql> select version();
+--------------------------------+
| version()                      |
+--------------------------------+
| 5.1.18-beta-valgrind-max-debug |
+--------------------------------+
1 row in set (0.00 sec)

mysql> set global general_log=1;
Query OK, 0 rows affected (0.00 sec)

mysql> select 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.00 sec)

mysql> select version();
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    1
Current database: mysql

+---------------------------+
| version()                 |
+---------------------------+
| 5.0.40-valgrind-max-debug |
+---------------------------+
1 row in set (0.01 sec)

mysql> select * from mysql.general_log;
ERROR 2013 (HY000): Lost connection to MySQL server during query

How to repeat:
See description.
[18 Apr 2007 9:02] Sveta Smirnova
Thank you for the report.

Verified as described.
[1 Aug 2008 5:58] Giuseppe Maxia
this is not a bug, IMO.
moving tables back and forth across MySQL versions has never been recommended. 

http://dev.mysql.com/doc/refman/5.1/en/downgrading.html
"If you downgrade from one release series to another, there may be incompatibilities in table storage formats. In this case, you can use mysqldump to dump your tables before downgrading. After downgrading, reload the dump file using mysql or mysqlimport to re-create your tables"