Bug #6096 field.max_length is always zero for numeric columns (stmt_resultset_metadata)

• Submitted: 14 Oct 2004 12:44
• Modified: 28 Oct 2004 13:10
• Reporter: Georg Richter
• Status: Closed
• Category: MySQL Server
• Severity: S1 (Critical)
• Version: 4.1
• OS: Linux (Linux)
• Assigned to: Konstantin Osipov
• CPU Architecture: Any

[14 Oct 2004 12:44] Georg Richter

Description:
When retrieving resultset metadata from a prepared statement field->max_length is always zero for 
numerical values. 
 
Output: 
Max. Lenghts (PS) 
Field 1: Len:20  max. Len: 8 
Field 2: Len:11  max. Len: 0 
Lenghts (Query) 
Field 1: Len:20  max. Len: 8 
Field 2: Len:11  max. Len: 4 

How to repeat:
#include <mysql.h> 
#include <stdio.h> 
 
main() { 
	MYSQL		*mysql; 
	MYSQL_STMT	*stmt; 
	MYSQL_RES	*result; 
	char        query[512]; 
	int			i; 
    int         val = 1; 
 
	mysql = mysql_init(NULL); 
	 
	if (!mysql_real_connect(mysql, "localhost", "root", "", "test", 0, NULL, 0)) { 
		printf("Error: %s\n", mysql_error(mysql)); 
		mysql_close(mysql); 
		exit(-1); 
	} 
	/* create a temporary table */ 
    mysql_query(mysql, "CREATE TEMPORARY TABLE t1 (a varchar(20), c2 int)"); 
 
    /* insert some values */ 
    mysql_query(mysql, "INSERT INTO t1 VALUES ('foo',2),('bar(kov)',4000)"); 
 
    stmt = mysql_stmt_init(mysql); 
    strcpy(query, "SELECT * FROM t1"); 
    mysql_stmt_prepare(stmt, query, strlen(query)); 
    mysql_stmt_execute(stmt); 
    mysql_stmt_attr_set(stmt, STMT_ATTR_UPDATE_MAX_LENGTH, (void *)&val); 
    mysql_stmt_store_result(stmt); 
    result = mysql_stmt_result_metadata(stmt); 
     
    printf("Max. Lenghts (PS)\n"); 
    for (i=0; i < 2; i++) { 
        printf("Field %d: Len:%d  max. Len: %d\n", i+1, result->fields[i].length,  
                result->fields[i].max_length); 
    } 
 
    mysql_stmt_free_result(stmt); 
    mysql_stmt_close(stmt); 
 
    mysql_query(mysql, query); 
    result = mysql_store_result(mysql); 
 
    printf("Lenghts (Query)\n"); 
    for (i=0; i < 2; i++) { 
        printf("Field %d: Len:%d  max. Len: %d\n", i+1, result->fields[i].length,  
               result->fields[i].max_length); 
    } 
     
    mysql_free_result(result); 
 
   mysql_close(mysql); 
}

[28 Oct 2004 13:10] Konstantin Osipov

Fixed in 4.1.8
Subject: bk commit - 4.1 tree (konstantin:1.2056) BUG#6096

ChangeSet
  1.2056 04/10/27 22:53:50 [e-mail] +3 -0
  A fix and test case for  Bug#6096 "field.max_length is always zero for
  numeric columns (stmt_resultset_metadata)"
  libmysql/libmysql.c
    1.275 04/10/27 22:53:46 [e-mail] +19 -2
    A fix for Bug#6096 "field.max_length is always zero for numeric columns
     (stmt_resultset_metadata)": set field->max_lenght for numeric
    columns when we set up skip_result functions. A minor drawback for this
    approach is that field->max_length  can be not zero even if
    STMT_ATTR_UPDATE_MAX_LENGTH is not set.