MySQL - Where clause processing order

This is a basic question. I inherited some code containing a cfquery. It runs on CF9 with MySQL 5.6. The cfquery reads:

SELECT some_columns 
FROM   tablename 
WHERE  itemname = 'itemnamevar' 
AND    id > 0 
ORDER BY orderby

The table contains more than 20000 items. ID is the primary key autoincrement value. It looks to me like the previous coder used to put id > 0 into the query to prepend some other clause conditions to the query. If none of them are used (controlled by some if/else), the id > 0 should cause all data from the table to be selected.

So the code is used as:

SELECT some_columns
FROM   tablename
WHERE 
<cfif id>
   id = '###'
<cfelse>
   <cfif LEN(itemname)>
      itemname = 'itemnamevar' AND 
   </cfif>
   <cfif LEN(itemgroup)>
      itemgroup = 'itemgroupvar' AND 
   </cfif>
   id > 0
</cfif>

My question is: if all the other clauses minimize the query set, before the id > 0 is processed, can I assume the id > 0 will have no effect on performance or should I rewrite the code to remove that condition? This will take some time because there are plenty of queries to optimize.

I need to say that the website running this code has some heavy load (more than 200k visitors a month growing relatively quick).

Thanks in advance. Please let me know if you need further information.

Solution

Use an expression that evaluates to TRUE without checking at the data. For example:

1 = 1