1. In a computing environment, a system capable of substantially equally efficient look-up in both a first and second dimension space of a sparse dataset structure, even when the sparse dataset structure has been organized and stored for efficient access in the first dimension space but not in the second dimension space, thus creating a more efficient system for accessing data in the second dimension space than previous systems, wherein the sparse dataset structure comprises a first dimension space vector for each first dimension space in a dataset that has at least one significant value, each first dimension space vector comprising data values for first dimension spaces of the dataset, the sparse data structure comprising one or more sparse first dimension space vectors for sparse first dimension spaces in the dataset, and wherein for each first dimension space vector that is a sparse first dimension space vector, the first dimension space vector includes: a look-up index array where entries in the look-up index array represent second dimension spaces in the dataset; and a value array where each entry in the value array comprises a value of an entry of a second dimension space in the first dimension space vector, and wherein each entry in the value array corresponds to a second dimension space entry in the look-up index array, the system comprising: one or more processors; one or more computer readable media coupled to the one or more processors; a side structure implemented in the one or more computer readable media, wherein the side structure comprises: a first dimension space index; and a second dimension space index, wherein the second dimension space index comprises a location for each second dimension space in the dataset where a location can have an entry for a corresponding second dimension space and where an entry for a given second dimension space points to a location in the first dimension space index that has an entry that identifies a first dimension space that has a first significant entry for the given second dimension space; and wherein the first dimension space index comprises an entry for each significant entry in the sparse dataset organized by second dimension spaces.