MySQL Bugs: #18827: It is very slowly when the where statment include function

Bug #18827	It is very slowly when the where statment include function
Submitted:	6 Apr 2006 5:46	Modified:	6 Apr 2006 10:48
Reporter:	lucols lucols	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Server	Severity:	S2 (Serious)
Version:	5.0	OS:	Any (all)
Assigned to:		CPU Architecture:	Any

Description:
create table ab(id  int(11) NOT NULL auto_increment, code varchar(16),
status integer, PRIMARY KEY  (`ID`)  ) ;

insert 20000 row data ;

select like this:
select count(id) from ab where status=5;
It is very fase abut 2 seconds. 

Then use function in where condition,like this:
Create Function: CREATE FUNCTION `getStatus`(valueKey varchar(32)) RETURNS int(11)
BEGIN 
IF valueKey='REGISTERED' THEN
        return 5;
ELSEIF valueKey='FIRE' THEN
       return 6;
ELSE
     return 0;
END IF;
END

select count(id) from ab where status=getStatus('REGISTERED');
 
It will cost more time, may be 3 minutes.

I use mysqlcheck and all tables is OK.

So Bug or real performance ? and who can tell me how slove this problem?

How to repeat:
HARDWARE :  HP ML150, 1G RAM /2.1 XENO  CPU/ 73G SCSI HD 
OS: REDHAT AS 4

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