| Bug #12363 | character_set_results is nullable, but value_ptr returns string "NULL" | ||
|---|---|---|---|
| Submitted: | 3 Aug 2005 23:41 | Modified: | 13 Sep 2005 22:45 |
| Reporter: | Timothy Smith | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server | Severity: | S2 (Serious) |
| Version: | 4.1 | OS: | Any (any) |
| Assigned to: | Alexander Barkov | CPU Architecture: | Any |
[4 Aug 2005 0:33]
Timothy Smith
This patch makes it work - but I bet it's not quite correct.
12:31 ~/m/41/a$ bk diffs -u sql
===== sql/set_var.cc 1.169 vs edited =====
--- 1.169/sql/set_var.cc 2005-07-29 10:37:00 +12:00
+++ edited/sql/set_var.cc 2005-08-04 12:29:21 +12:00
@@ -1603,8 +1603,14 @@
Item_string *tmp;
pthread_mutex_lock(&LOCK_global_system_variables);
char *str= (char*) value_ptr(thd, var_type, base);
- tmp= new Item_string(str, strlen(str),
- system_charset_info, DERIVATION_SYSCONST);
+ if (!str)
+ {
+ tmp= new Item_empty_string("", 0);
+ tmp->null_value= 1;
+ }
+ else
+ tmp= new Item_string(str, strlen(str),
+ system_charset_info, DERIVATION_SYSCONST);
pthread_mutex_unlock(&LOCK_global_system_variables);
return tmp;
}
@@ -1894,7 +1900,7 @@
LEX_STRING *base)
{
CHARSET_INFO *cs= ci_ptr(thd,type)[0];
- return cs ? (byte*) cs->csname : (byte*) "NULL";
+ return cs ? (byte*) cs->csname : NULL;
}
[30 Aug 2005 12:15]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/internals/29026
[5 Sep 2005 7:48]
Alexander Barkov
Fixed in 4.1.15 and 5.0.13
[13 Sep 2005 22:45]
Mike Hillyer
Documented in 5.0.13 and 4.1.15 changelogs:
<listitem>
<para>
The value of <literal>character_set_results</literal> could be set to <literal>NULL</literal>,
but returned the string <literal>"NULL"</literal> when retrieved. (Bug #12363)
</para>
</listitem>
Description: See "How to repeat" section. How to repeat: I tested this with a fresh BK pull, on FreeBSD 5.0.4. 11:32 ~/m/41/m$ mysql test -e 'select version(); set character_set_results = NULL; select ifnull(@@character_set_results, "it really is null") as foo' +------------------+ | version() | +------------------+ | 4.1.14-debug-log | +------------------+ +------+ | foo | +------+ | NULL | +------+ It seems that character_set_results is the only nullable system variable. This caused the customer a problem when processing the mysqldump output with Java; the @OLD_CHARACTER_SET_RESULTS variable gets set to the string "NULL", and then when trying to reset @@CHARACTER_SET_RESULTS, it is of course an error that there is no character set named "NULL". Suggested fix: I tried editing sql/set_var.cc:sys_var_character_set::value_ptr() to return NULL instead of "NULL" , but it segfaults: 0x080b3044 in sys_var::item (this=0x848c0d4, thd=0xa1fe018, var_type=170040400, base=0x0) at item.h:731 731 { (gdb) bt full #0 0x080b3044 in sys_var::item (this=0x848c0d4, thd=0xa1fe018, var_type=170040400, base=0x0) at item.h:731 str = 0x0 #1 0x08066f2e in Item_func_get_system_var::fix_fields (this=0xa2290b0, thd=0xa1fe018, tables=0x0, ref=0xa2291e4) at item_func.cc:2891 _db_func_ = 0xbf1c554c "�U\034�y\t\006\b�\220\"\n\030�\037\n" _db_file_ = 0xa1fe56c "\030\214M\b\030�!\n\0300\"\n\030�!\n\030�!\n\017" item = (class Item *) 0x83086e8 _db_level_ = 3206305108 _db_framep_ = (char **) 0x7 #2 0x08060979 in Item_func::fix_fields (this=0xa2291a8, thd=0xa1fe018, tables=0x0, ref=0xa229224) at item_func.cc:155 item = (class Item *) 0xa2291a8 arg = (class Item **) 0xa2291e4 arg_end = (class Item **) 0xa2291ec buff = "\000\000\000\000d\233\"\n\034V\034�@�\037\n\000\000\000\000d\233\"\n\034V\034�w�\r\b/\t\000\000�U\034��U\034��U\034�\000\000\000\000�\220\"\n�U\034�\001\000\000" __func__ = "fix_fields" #3 0x080dd446 in setup_fields (thd=0xa1fe018, ref_pointer_array=0xa229c00, tables=0x0, fields=@0xa229c00, sum_func_list=0xa229b64) at sql_base.cc:2438 _db_func_ = 0x9ca <Error reading address 0x9ca: Bad address> _db_file_ = 0xbf1c560c ",V\034�@�\037\n@\222\"\nd\233\"\n�V\034�\r%\016\b\030�\037\n" ref = (class Item **) 0xa229c00 item = (class Item *) 0xa2291a8 it = {<base_list_iterator> = {list = 0xa1fe1a8, el = 0xa229220, prev = 0xa1fe1a8, current = 0xa229220}, <No data fields>} _db_level_ = 3206305296 _db_framep_ = (char **) 0xbf1c5614 set_query_id = Error accessing memory address 0x0: Bad address.