1. A method comprising: receiving a first query that specifies a first object identifier; and if a first query plan exists that implements the first query, except that the first query plan does not comprise the first object identifier and instead comprises a parameter marker in place of the first object identifier, creating a first query execution plan from the first query plan, substituting the first object identifier in the first query execution plan for the parameter marker, and executing the first query execution plan to read a first object identified by the first object identifier; if a run time of the execution of the first query execution plan is more than a threshold amount longer than run times of all other query execution plans that match the first query execution plan except for the object identifier, building a new query plan for the first query, wherein the new query plan comprises the first object identifier; and if the new query plan is identical to the first query plan except that the new query plan comprises the first object identifier in place of the parameter marker, deleting the new query plan.