I am using hibernate.hbm2ddl.auto=update in production environment,hibernate will generate a random name for every unique key,it will cerate a new unique key everytime when application started,It's stupid and break compatibility with previous version.please use UK_md5hex(column1[,column2[,column3...]]) as the key name,so the hibernate.schema_update.unique_constraint_strategy = RECREATE_QUIETLY will be the same behaviour as "create if not exists".