Optimization level

You normally obtain optimum overall performance with the default optimization level, HIGH. The time that it takes to optimize the statement is usually unimportant. However, if experimentation with your application reveals that your query is still taking too long, you can set the optimization level to LOW.

If you change the optimization level to LOW, check the SET EXPLAIN output to see if the optimizer chose the same query plan as before.

To specify a HIGH or LOW level of database server optimization, use the SET OPTIMIZATION statement.