1. One or more computer storage media storing computer-useable instructions that, when used by one or more computing devices, cause the one or more computing devices to perform a method comprising: receiving an input query expression and a set of one or more physical property requirements, the input query expression being represented as an operator tree comprising a plurality of logical operators; performing logical exploration by applying transformation rules to generate a plurality of logical query expressions with varying logical operators; performing physical optimization for each logical query expression by applying implementation rules to convert logical operators to physical operators, wherein physical optimization comprises: for each physical operator considered for each logical operator, determining delivered structural properties output by the physical operator, the delivered structural properties including a partitioning property, a sorting property, and a grouping property, for each physical operator considered for each logical operator, determining required structural properties as inputs for the physical operator, the required structural properties including a partitioning property, a sorting property, and a grouping property, determining whether delivered structural properties satisfy corresponding required structural properties, and identifying valid execution plans in which delivered structural properties satisfy required structural properties; estimating costs associated with each of the valid execution plans; and selecting, from the valid execution plans, an execution plan having a lowest cost as an optimized execution plan.