Bug #6738 "Use_count: Wrong count for key at" messages in server output
Submitted: 21 Nov 2004 9:44 Modified: 29 Sep 2008 19:11
Reporter: Sergey Petrunya Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server Severity:S3 (Non-critical)
Version:5.0-bk OS:Any
Assigned to: Sergey Petrunya CPU Architecture:Any

[21 Nov 2004 9:44] Sergey Petrunya
Description:
When executing some types of queries (example below) the following messages appear in server output:

[Note] Use_count: Wrong count for key at 0x8a5d938, 4 should be 6
[Note] Use_count: Wrong count for key at 0x8a5d2b8, 4 should be 6

The query results seem to be correct though, and no memory leaks are reported. 

(Hakan had this too, with different numbers in "X should be Y")

How to repeat:
CREATE TABLE `t1` (
  `a` int(11) default NULL,
  `b` int(11) default NULL,
  `c` int(11) default NULL,
  `d` int(11) default NULL,
  `filler1` char(200) default NULL,
  `filler2` char(200) default NULL,
  KEY `a` (`a`,`b`,`c`,`d`)
) ENGINE=MyISAM;

insert into t1(a,b,c,d) values (1,1,1,1);
insert into t1(a,b,c,d) values (2,2,2,2);
insert into t1(a,b,c,d) values (3,3,3,3);

explain select * from t1 where a IN (1,2) and b IN (1,2,3)  and c IN (5,7);

and look at server log.

Suggested fix:
Figure out what this is.
[4 Jul 2006 16:22] Sergey Petrunya
This problem was fixed in fix for BUG#16168
[29 Sep 2008 19:11] Konstantin Osipov
As indicated in the comment, the problem is fixed.