1. A method for use in a database system, comprising: receiving, by a filter executing on at least one processor, an incoming request to perform an operation in the database system; receiving, by the filter from an optimizer, a resource estimate relating to the incoming request; determining, by the filter, whether the resource estimate exceeds an available resource of the database system; in response to determining that the resource estimate exceeds the available resource of the database system, the filter rejecting the incoming request prior to execution of the incoming request in the database system; monitoring, by a regulator executing on the at least one processor, execution of requests in the database system; and in response to determining that the resource estimate does not exceed the available resource of the database system, allowing the incoming request to execute, and adjusting, by the regulator, a priority setting of the incoming request during execution of the incoming request based on the monitored execution and the resource estimate.