MySQL Bugs: #9378: Accessing data from local and remote application

Bug #9378	Accessing data from local and remote application
Submitted:	24 Mar 2005 9:46	Modified:	24 Mar 2005 16:57
Reporter:	Carmelo R. Cartiere	Email Updates:
Status:	Can't repeat	Impact on me:	None
Category:	MySQL Server	Severity:	S1 (Critical)
Version:	4.0.14	OS:	Windows (Win2k/Win2003 Server)
Assigned to:		CPU Architecture:	Any

Description:
I have a database installation on a Win2003 server on which runs an application using the libmysql library for having access to records. My application executes the following statement "SELECT MAX( private_record_id ) FROM table WHERE condition" to retrieve the last "private_record_id" provided. So, if no result is returned, to the first record being inserted is assigned "private_record_id=1'.
The thing is that if the application tryies to access the database from a remote location (from a Win2000 server) everything works fine. But if the application is accessing locally (on the Win2003 server) it doesn't work: no rows are retrieved though the database is filled with data.
To verify, I tryed to execute the statement through MySQL Control Center and everything works fine on the both local and remote side. Then I thinked that there could be a returning error and tried to trap it within the application... but no errors are returned...

How to repeat:
Don't know... it is a very strange issue...

Could you please provide a complete test case (code + table schema + dump).
Thanks in advance.

Uploaded the code and table schema. Hope this can help.

Don't know how to provide a dump. Further, the issue is not repeatable on my side (i work on the remote session that is fine working and have the database on the Win2003 server at 800 miles) and when the error is occurring there are no return codes. If I can provide you with some other specifics just ask.

You can create a dump of your table using the client tool called mysqldump
i.e:

c:\mysql\bin>mysqldump -uroot mydb mytbl > mydump.sql

c:\mysql\bin>type mydump.sql
-- MySQL dump 10.9
--
-- Host: localhost    Database: mydb
-- ------------------------------------------------------
-- Server version       4.1.10-nt

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

--
-- Table structure for table `mytbl`
--

DROP TABLE IF EXISTS `mytbl`;
CREATE TABLE `mytbl` (
  `id` int(11) default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

--
-- Dumping data for table `mytbl`
--

/*!40000 ALTER TABLE `mytbl` DISABLE KEYS */;
LOCK TABLES `mytbl` WRITE;
INSERT INTO `mytbl` VALUES (1),(2);
UNLOCK TABLES;
/*!40000 ALTER TABLE `mytbl` ENABLE KEYS */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

table dump

Attachment: mydump.sql (text/plain), 12.45 KiB.

Great. Added the dump file. Thank you for supporting.

Think I got the bug. Carefully reviewing the code that I sent to you I noticed that while fetching the record with mysql_fetch_row, I used a global variable instead of the local one which had the returning address from the SELECT statement (OpenMySQLTable function).
Sorry for bothering you though I enjoyed your help and it was precious to me for keeping me on the part of code I sent to you. Thanks a lot.

I wasn't able to repeat. Using the mysql client:

c:\mysql\bin>mysql -uroot bug9378
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 11 to server version: 4.0.23-nt

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> select max(nr) from ordini where modello = 'PERA';
+---------+
| max(nr) |
+---------+
|      96 |
+---------+
1 row in set (0.01 sec)

and doing the same with the C application at the bottom:

C:\temp>bug9378
Connected with the Server: 4.0.23-nt
Query:  SELECT MAX(nr) FROM ordini WHERE modello = 'PERA'
Number of records found:  1
Record #1:-
  Fld #1 (MAX(nr)): 96
==========================================

#include <stdio.h>
#include <string.h>
#include <my_global.h>
#include <m_ctype.h>
#include <m_string.h>
#include <mysql.h>

#define MyQuery "SELECT MAX(nr) FROM ordini WHERE modello = 'PERA'"

void main()
{
  
  MYSQL *MySQL;
  MYSQL_RES	* res ;
  int			i, j, k, l, x ;
  MYSQL_FIELD	* fd ;
  MYSQL_ROW	row ;
  char	aszFlds[ 25 ][ 25 ] ;

  if ( (MySQL = mysql_init((MYSQL*) 0)) && 
       mysql_real_connect( MySQL,"localhost","root",
                           "",	"bug9378",	0, NULL, 0 ))
       printf("Connected with the Server: %s\n",
            mysql_get_server_info(MySQL));
  else
  {
    printf("Failed to connect with the server\n");
    mysql_close( MySQL );
    return;
  }
   
  if ( ! mysql_query( MySQL, MyQuery ) )
  {
    res = mysql_store_result( MySQL ) ;
    i = (int) mysql_num_rows( res ) ; l = 1 ;
    printf( "Query:  %s\nNumber of records found:  %ld\n", MyQuery, i ) ;
    
    for ( x = 0 ; fd = mysql_fetch_field( res ) ; x++ )
       strcpy( aszFlds[ x ], fd->name ) ;
    
    while ( row = mysql_fetch_row( res ) )
    {
      j = mysql_num_fields( res ) ;
      printf( "Record #%ld:-\n", l++ ) ;
      
      for ( k = 0 ; k < j ; k++ )
	       printf( "  Fld #%d (%s): %s\n", k + 1, aszFlds[ k ],
		            (((row[k]==NULL)||(!strlen(row[k])))?"NULL":row[k])) ;
         puts( "==========================================\n" ) ;
    }
      
    mysql_free_result( res ) ;
  }
  else 
   printf( "Sorry Query Failed\n" ) ;

   mysql_close(MySQL);
   return;
}