[MDEV-6093] CHECK reports 'Corrupt' with CONNECT Created: 2014-04-14  Updated: 2020-07-29  Resolved: 2020-07-29

Status: Closed
Project: MariaDB Server
Component/s: Storage Engine - Connect
Affects Version/s: 10.0.10
Fix Version/s: 10.4.12, 10.1.45, 10.2.32, 10.3.23, 10.5.4

Type: Bug Priority: Minor
Reporter: Federico Razzoli Assignee: Olivier Bertrand
Resolution: Fixed Votes: 1
Labels: None


 Description   

Some administrative commands report corruption for CONNECT tables:

  • CHECK TABLE
  • REPAIR TABLE
  • ANALYZE TABLE
  • others?

For example:

MariaDB [test]> CHECK TABLE tc;
 
+---------+-------+----------+------------------------------------------------------------------------+
 
| Table   | Op    | Msg_type | Msg_text                                                               |
 
+---------+-------+----------+------------------------------------------------------------------------+
 
| test.tc | check | Error    | CONNECT Unsupported command                                            |
 
| test.tc | check | Error    | Can't lock file (errno: 122 "Internal (unspecified) error in handler") |
 
| test.tc | check | error    | Corrupt                                                                |
 
+---------+-------+----------+------------------------------------------------------------------------+
 
3 rows in set (0.00 sec)

I understand that they are not supported. The problem is with the last row. If you want a program to verify whether a table is corrupted, you issue CHECK TABLE and look if the last returned row has Msg_type='error' and Msg_text='Corrupt'. You do the same if you want the program to try a REPAIR and check if it succeeds.

It would be nice if CONNECT could avoid returning that row.

 Comments   
Comment by Federico Razzoli [ 2014-04-14 ]

For example, if it could do something like this (InnoDB), it would be perfect:

MariaDB [test]> REPAIR TABLE t;
 
+--------+--------+----------+---------------------------------------------------------+
 
| Table  | Op     | Msg_type | Msg_text                                                |
 
+--------+--------+----------+---------------------------------------------------------+
 
| test.t | repair | note     | The storage engine for the table doesn't support repair |
 
+--------+--------+----------+---------------------------------------------------------+
 
1 row in set (0.00 sec)

Comment by Elena Stepanova [ 2014-04-14 ]

CHECKSUM returns the first two, but not 'Corrupt'.
Interestingly, OPTIMIZE behaves nice:

+---------+----------+----------+-----------------------------+
 
| Table   | Op       | Msg_type | Msg_text                    |
 
+---------+----------+----------+-----------------------------+
 
| test.t1 | optimize | Warning  | CONNECT Unsupported command |
 
| test.t1 | optimize | status   | OK                          |
 
+---------+----------+----------+-----------------------------+

Comment by Olivier Bertrand [ 2014-04-15 ]

Here is what I get with the last version of CONNECT:

MariaDB [connect]> CHECK TABLE employe;
 
+-----------------+-------+----------+------------------------------------------------------------------------+
 
| Table           | Op    | Msg_type | Msg_text                                                               |
 
+-----------------+-------+----------+------------------------------------------------------------------------+
 
| connect.employe | check | Error    | CONNECT Unsupported command                                            |
 
| connect.employe | check | Error    | Can't lock file (errno: 122 "Internal (unspecified) error in handler") |
 
| connect.employe | check | error    | Corrupt                                                                |
 
+-----------------+-------+----------+------------------------------------------------------------------------+
 
3 rows in set (0.08 sec)
 
 
 
MariaDB [connect]> REPAIR TABLE employe;
 
+-----------------+--------+----------+------------------------------------------------------------------------+
 
| Table           | Op     | Msg_type | Msg_text                                                               |
 
+-----------------+--------+----------+------------------------------------------------------------------------+
 
| connect.employe | repair | Error    | CONNECT Unsupported command                                            |
 
| connect.employe | repair | Error    | Can't lock file (errno: 122 "Internal (unspecified) error in handler") |
 
| connect.employe | repair | error    | Corrupt                                                                |
 
+-----------------+--------+----------+------------------------------------------------------------------------+
 
3 rows in set (0.00 sec)
 
 
 
MariaDB [connect]> ANALYZE TABLE employe;
 
+-----------------+---------+----------+------------------------------------------------------------------------+
 
| Table           | Op      | Msg_type | Msg_text                                                               |
 
+-----------------+---------+----------+------------------------------------------------------------------------+
 
| connect.employe | analyze | Error    | CONNECT Unsupported command                                            |
 
| connect.employe | analyze | Error    | Can't lock file (errno: 122 "Internal (unspecified) error in handler") |
 
| connect.employe | analyze | error    | Corrupt                                                                |
 
+-----------------+---------+----------+------------------------------------------------------------------------+
 
3 rows in set (0.00 sec)
 
 
 
MariaDB [connect]> OPTIMIZE TABLE employe;
 
+-----------------+----------+----------+----------+
 
| Table           | Op       | Msg_type | Msg_text |
 
+-----------------+----------+----------+----------+
 
| connect.employe | optimize | status   | OK       |
 
+-----------------+----------+----------+----------+
 
1 row in set (0.05 sec)
 
 
 
MariaDB [connect]> CHECKSUM TABLE employe;
 
+-----------------+----------+
 
| Table           | Checksum |
 
+-----------------+----------+
 
| connect.employe |     NULL |
 
+-----------------+----------+
 
1 row in set, 2 warnings (0.08 sec)

The problem is complex. CONNECT works by treating each query as a separate entity. For this, it needs to know when a new query begins. There are two functions that mark the start of new query for a table:

1 - external_lock: called when the table is not locked
2 - start_stmt: called when the table is locked

Therefore CONNECT does all query initialization and termination work in external_lock (most of the time) in particular checks whether the command is supported or not supported. When a command is not supported CONNECT prepares the message "CONNECT Unsupported command" and returns HA_ERR_INTERNAL_ERROR.

What happens next is MariaDB processing. The message "Can't lock file" comes from CONNECT doing things in external_lock that are not related to locking. I don't know where the "Corrupt" message comes from.

This shows that some plugins, in particular CONNECT, need a true function call at the beginning of each new query. The start_stmt function would be all right if unconditionally called.

Comment by Chris Calender (Inactive) [ 2017-01-26 ]

Also reports this for mysql_upgrade:

db1.t1
Error : CONNECT Unsupported command
Error : Got error 122 'CONNECT Unsupported command' from CONNECT
error : Corrupt
db1.t2
Error : CONNECT Unsupported command
Error : Got error 122 'CONNECT Unsupported command' from CONNECT
error : Corrupt

Comment by Olivier Bertrand [ 2020-07-29 ]

Reopening this report, I found that this had been fixed. Why not closed yet? Perhaps because it was not tested on all cases and platforms. Anyway I close it and reopen it if it fais again.

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