16. The one or more non-transitory storage media of claim 15 , wherein the one or more factors specified by the query plan formation data further includes a reason why the particular query rewrite optimization failed to eliminate an operator of said one or more operators.
16. The one or more non-transitory storage media of claim 15 , wherein the one or more factors specified by the query plan formation data further includes a reason why the particular query rewrite optimization failed to eliminate an operator of said one or more operators. 20. The one or more non-transitory storage media of claim 16 , the one or more sequences of instructions comprising instructions that, when executed by said one or more computing devices, cause: in response to determining that one or more query rewrite optimizations failed to eliminate one or more operators from the query plan, determining not to execute the query plan.