1. A method comprising: in response to receiving a query that aggregates data from at least one database object, of a plurality of database objects: creating one or more storage containers, each corresponding to one or more set identifiers of a plurality of set identifiers; wherein mapping data maps each set identifier, of the plurality of set identifiers, to one or more key values that respectively identify one or more rows storing a particular unique combination of values, each value of said particular unique combination of values occurring in a different column on which data is grouped in the query; evaluating the query; wherein evaluating the query comprises aggregating the data from the at least one database object; wherein aggregating the data comprises: analyzing a particular row of the at least one database object, wherein the particular row includes a particular key value that is mapped, in the mapping data, to a particular set identifier, locating at least one storage container, of the one or more storage containers, that corresponds to the particular set identifier, and aggregating data, from the particular row of the at least one database object, within the at least one storage container; wherein the method is performed by one or more computing devices.