1. A method for improving query performance in a data warehousing environment, the method comprising: splitting data as part of an extract-transform-load (ETL) process in a data warehousing environment, the data extracted from a data source and split into: a first set of split data portions based on a first attribute of the extracted data, the first set of split data portions configured to be used as a source for a first set of target relvars; and a second set of split data portions based on a second attribute of the extracted data, the second set of split data portions configured to be used as a source for a second set of target relvars, the second attribute being different from the first attribute, wherein data within each set of relvars is organized according to an inquiry restricted by at least one of the first attribute or the second attribute; using the first and second split data portions to refresh corresponding target relvars; wherein as a result of the refreshing the first and second set of target relvars, a same portion of the data from the data source is contained within each of the first and second sets of target relvars, and the same portion of data is arranged differently in the first set of target relvars than in the second set of target relvars; wherein each of the first and second target relvars are one of a database table or a partition of a database table; saving the first and second sets of split data portions for comparison with sets of split data portions created by splitting a later set of extracted data from the data source; comparing the first and second split data portions with a previously saved version of the first and second sets of split data portions to identify modified split data portions; and propagating the modified split data portions for refreshing the first and second set of target relvars.