16. A computer-readable non-transitory storage medium storing instructions, wherein the instructions include instructions which, when executed by one or more processors, cause the one or more processors to perform steps of: from a workload set, identifying a plurality of database query language statements for automatic tuning, wherein the workload set comprises database query language statements and current performance data for the database query language statements; executing each database query language statement from said plurality of query language statements against a database; collecting new performance data from said executing each database query language statement, said collecting comprising measuring resource usage by said executing each database query language statement; detecting that conditions in said database that affect executing said plurality of database query language statements changed based at least in part on comparison of the new performance data with the current performance data; in response to the detecting, tuning a subset of database query language statements from said plurality of database query language statements, said subset of database query language statements comprising a database query language statement from said plurality of database query language statements, wherein the new performance data is different from the current performance data for the database query language statement; wherein the tuning the subset of database query language statements comprises generating a plurality of tuning recommendations for execution of the subset of database query language statements; testing the plurality of tuning recommendations against said database, wherein the testing the plurality of tuning recommendations comprises, for each tuning recommendation of said plurality of tuning recommendations: executing a respective database query language statement from said subset of database query language statements with said each tuning recommendation enabled; measuring resource usage by said executing the respective database query language statement with said each tuning recommendation enabled, wherein the resource usage comprises processor time or buffer gets; and measuring benefits based on performance improvement of said executing the respective database query language statement with said each tuning recommendation enabled; based on the testing, determining a subset of said plurality of tuning recommendations resulted in performance improvement that meets a specific set of criteria; and implementing the subset of said plurality of tuning recommendations.
19. The computer-readable storage medium of claim 16 , wherein the subset of database query language statements are prioritized, the instructions further comprising instructions for: automatically tuning the subset of database query language statements in order of priority.