1. A method comprising: in response to receiving a first query, generating a first execution plan that is used to execute the first query and that involves accessing a particular database object; executing the first query by executing the first execution plan; determining a change metric that is associated with the particular database object at a first time; receiving a second query, wherein the first execution plan may be used to execute the second query; based on the change metric, determining whether to generate an execution plan for the second query; wherein the method is performed by one or more computing devices.