[MDEV-4771] Connect SE: Connection dies using table_type=pivor Created: 2013-07-09  Updated: 2013-07-12  Resolved: 2013-07-12

Status: Closed
Project: MariaDB Server
Component/s: None
Affects Version/s: 10.0.3
Fix Version/s: 10.0.4

Type: Bug Priority: Minor
Reporter: erkan yanar Assignee: Olivier Bertrand
Resolution: Fixed Votes: 0
Labels: connect-engine
Environment:

Linux/Ubuntu/Precise/LXContainer


 Description   

Creating a pivot table (Connect SE) and selecting from the table works.
Doing a second select the connection dies.

 MariaDB [test]> select * from pivottet;
 
ERROR 2013 (HY000): Lost connection to MySQL server during query
 

MariaDB [test]> create table pivottet engine=connect table_type=pivot tabname=salary;
 
Query OK, 0 rows affected (0.02 sec)
 
MariaDB [test]> select * from pivottet;
 
+--------+------+-----+------+-----+
 
| sellet | 1    | 2   | 3    | 4   |
 
+--------+------+-----+------+-----+
 
|      1 |  100 | 300 | 1000 |   0 |
 
|      2 | 1000 | 100 |    0 |   0 |
 
|      3 |    0 |   0 |    0 | 500 |
 
+--------+------+-----+------+-----+
 
3 rows in set (0.00 sec)
 
MariaDB [test]> select * from pivottet;
 
ERROR 2013 (HY000): Lost connection to MySQL server during query

That is written into the error log:

Jul  9 10:17:56 localhost mysqld: 130709 10:17:56 [Warning] Aborted connection 264 to db: 'test' user: 'root' host: 'localhost' (Unknown error)

Regards
Erkan

 Comments   
Comment by Olivier Bertrand [ 2013-07-10 ]

I could not reproduce such error with the current version of CONNECT.

Do debug I need to know exactly what was executed and, in particular, to
have the salary table.
How can I get that from Erkan?

Regards, Olivier

Comment by erkan yanar [ 2013-07-10 ]

like that:

#v
CREATE TABLE `salary` (
`sellet` int(11) DEFAULT NULL,
`company` int(11) DEFAULT NULL,
`volume` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
#v-

Comment by Olivier Bertrand [ 2013-07-10 ]

Thanks, I shall work on it.
Regards,
Olivier

Comment by Olivier Bertrand [ 2013-07-10 ]

Cannot reproduce on Windows and ubuntu

Comment by erkan yanar [ 2013-07-10 ]

So it's 'gone' with the current version or some settings on my side.
Nevertheless Im gonna check the next mariadb release.

Comment by Olivier Bertrand [ 2013-07-11 ]

Sorry erkan, I wrongly thought it was working on ubuntu but it turned
out that it did not and disconnected on the second,
and further, tries to select the table. So this is not closed but not
going to be solved soon because I get no information
on the possible error. For instance, under GDB nothing is told, and
looking at the traces I have done, mysqld disconnects
even before creating the CONNECT thread supposed to handle the query!

Because of this, and also on some valgring warnings, the next version of
CONNECT will not support the PIVOT type, hoping
that will be temporarily...
Regards,
Olivier

Comment by Olivier Bertrand [ 2013-07-11 ]

Is indeed failing on Linux

Comment by Olivier Bertrand [ 2013-07-11 ]

Further investigation shows that this bug is related to the use of the query cache. Before this is fixed (by preventing queries on PIVOT tables to be cached, as for queries on partitioned tables) a bypass is to specify the query_cache_size variable to 0. This makes the query cache not used.

Comment by erkan yanar [ 2013-07-11 ]

Ahoi Olivier,
yes setting query_cache_size=0 worked.

Thx!

Comment by Olivier Bertrand [ 2013-07-12 ]

Because CONNECT works on external data that can be modified any time out of MariaDB, it must not use the query cache. Therefore, query cache has been permanently disabled for CONNECT tables.

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