Optimize | The statements is re-written into a set of semantically identical statements each of which is executed separately. The fastest one(s) are reported. Ideally used for queries with short execution time. |
Rewrite | The execution plans of re-written statements are compared. Unlike in optimize, the statements are not executed, thus ideal for queris with long execution time. |
Index | Creates virtual indexes before having the execution plan displayed. New queries are executed and performance is compared with old ones. |
Rewrite & Index | Combines Rewrite and Index. |