I've implemented the optimistic in mysql database using MD5 and SHA-1 and everything work well. My problem is that i don't know if this is the best solution as i don't know how much time mysql take to calculate each hash. Here is the method
select field1 , field2 ,sha1(field1),md5(field2) from mytable
where id = someValueHere
update mytable set column1=value1,column2=value2
where id= someValueHere
and sha1(field1) = storedValue
this method gives you the possibily to not touch your databse or make changes on it. But as i've mentionned i need to know more details about performance of this method.