MySQL Bugs: #6712: 4.1 Client drivers Segfault

Bug #6712	4.1 Client drivers Segfault - or malformed packets
Submitted:	19 Nov 2004 1:49	Modified:	29 Dec 2004 6:37
Reporter:	Jacques Amar	Email Updates:
Status:	No Feedback	Impact on me:	None
Category:	MySQL Server	Severity:	S1 (Critical)
Version:	4.1.7	OS:	Linux (Linux)
Assigned to:		CPU Architecture:	Any

Description:
The clients connections to Server 4.1.7 would segfault or give malformed packet errors AND slowly corrupt tables with updates.

The problem would appear after an INSERT. The statement:
"select * from tablename" would segfault, both in mysql client on host, remote and through perl DBI DBD::connection.

40 client linux server talking to a server exhibited this bahviour. A quick serach on the net showed I wasn't alone.

The solution was to regress the server back to 4.0.22

How to repeat:
Slow table (server) corruption on INSERTS.

Suggested fix:
Had to regress both clients and server to 4.0

Can you please add a little more information to this report?

E.g. are you using FULLTEXT indexes in the tables you insert to?

The tables did not have anything in particualr. The first one to go was:
CREATE TABLE `site` (
  `site_id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  `image` varchar(255) default NULL,
  `status` enum('active','deleted','pending') NOT NULL default 'pending',
  `url` varchar(255) default NULL,
  `old_id` char(2) default NULL,
  `created` int(11) unsigned NOT NULL default '0',
  `feature` int(1) NOT NULL default '0',
  `category_id` int(11) default NULL,
  `height` int(11) default NULL,
  `width` int(11) default NULL,
  `phrase` text,
  `homepage` varchar(255) default NULL,
  `second` varchar(255) default NULL,
  `third` varchar(255) default NULL,
  `fourth` varchar(255) default NULL,
  `fifth` varchar(255) default NULL,
  `urlext` enum('com','net') NOT NULL default 'com',
  `phrase1` varchar(255) default NULL,
  `phrase2` varchar(255) default NULL,
  `phrase3` varchar(255) default NULL,
  `phrase4` varchar(255) default NULL,
  `joinpage` varchar(255) default NULL,
  `long_description` text,
  `phrase5` varchar(255) default NULL,
  `phrase6` varchar(255) default NULL,
  `hg` int(1) unsigned NOT NULL default '0',
  `site_type` enum('standard','exclusive') default 'standard',
  `access_type` char(1) default 'B',
  `access_id` tinyint(1) unsigned default NULL,
  `site_alias` varchar(64) default NULL,
  PRIMARY KEY  (`site_id`),
  UNIQUE KEY `old_id` (`old_id`),
  KEY `category_id` (`category_id`)
) ;
After an INSERT
select * from site
would segfault - where as 
select * from site limit 10000000;
would work fine

Other tables got packet errors. Tried with 4.0 client AND 4.1 clients.

Major software interface uses perl. Tried the latest DBD::mysql and older versions.

The problem seems to be at the server side. I simply reinstalled 4.0.22 and ALL problems went away, with all clients.

This was a production system, so I couldn't afford to keep it alive to test more

I have tried with empty table and it works for me just fine.

Can you upload a table that crashes a connection to the 'Files' category of this bug record ?????

Please, I want to comment on this bug.

I also had this packet corruption issues either with Linux or Windows clients. I have come to a solution, though I don't know if this is the real solution. ;-) Either way, I think this problem is related to the compressed protocol. When I excluded the CLIENT_COMPRESS flag on the "mysql_real_connect" call, the problem go away! I will explain my problem further:

Seen on: MySQL server 4.1.4-gamma and 4.1.7-standard (LINUX, RedHat 9.0)
Linux client: libmysqlclient_r.so.14
Windows clients:
  - libmySQL.DLL (249.856 KBytes as shipped with 4.0 server, I think).
  - libmySQL.DLL (1.069.056 KBytes as shipped with 4.1.7 server).

As I'm using Windows and Linux clients and both showed this bug, I concluded this was related to the Database server, not the client libraries.

This is what happened:
I'm using InnoDB with extensive use of foreign keys. I'm linking the client libraries with my propietary C++ software.
 
A) Malformed packets:
Query:  "SELECT * FROM my_table WHERE id=1"
Result: With a fresh mySql server started, all was fine. After doing some INSERT statements, this query returned with error "Malformed packet". I have to say, a MySQL-Front end program returned the correct result.
 
B) Corrupted column names in result:
Query: "SELECT * FROM my_table"
Result: Corrupted column names in "mysql_fetch_fields(__result);" call. This was extremelly weird since doing "SELECT id, name FROM..." returned the correct column names. I though this problem is related to the A) above, since this could be also a corruption in the packets, though on a different position.
 
I hope this could be of any help.

Forget about my previous quote on the compressed client protocol: The problem persisted shortly after I posted the above message.

The only way to get the clients working again (after a "malformed packet" error) is restarting the full server.

I apologize for the "false positive", although the comments on the behaviour is still correct.

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".