19. The system of claim 11 , wherein the grid is a logarithmic-scale grid.
11. A system, comprising: a query interface configured to receive queries configured according to a query template, the query interface receiving a first query that includes values for a plurality of parameters of the query template, the first query comprising a plurality of efficiency expressions; a query plan manager that manages a plurality of query plans using a selectivity space. the query plan manager comprising: a selectivity region mapper being configured to map the first query to a first selectivity region in the selectivity space using at least one processor, the selectivity space being an array of selectivity regions arranged according to a grid having a number of dimensions equal to a number of efficiency expressions of the first query, the grid, in accordance with the plurality of efficiency expressions, comprising a multi-dimensional grid divided into a plurality of multi-dimensional regions forming the array of selectivity regions; a key generator being configured to generate a first key using the at least one processor for the first query that includes an indication of the first selectivity region; a query compiler caller being configured to request the first query to be compiled to generate a first query plan; the first query plan being stored in association with the first key; and the first query plan being executed with respect to the first query.