Time-HOBI
Jan Chmiel, Tadeusz Morzy, Robert Wrembel · 2010
One of the important research and technological problems in data warehousing is the optimization of star queries. So far, most of the research focused on optimizing such queries by means of join indexes and bitmap join indexes. In this paper we propose an index, called Time-HOBI, for optimizing star queries and computing aggregates along dimension hierarchies. Time-HOBI, created on a dimension hierarchy, is composed of: (1) a hierarchically organized bitmap index (HOBI), one bitmap index for one dimension level and (2) a time index (TI) that implicitly encodes time in every dimension. HOBI allows to quickly search for fact rows that fulfill selection criteria. With the support of TI joining a fact table with the Time dimension is avoided. Time-HOBI was implemented and evaluated experimentally on a real dataset, coming from the biggest East-European Internet auction platform Allegro.pl. The experiments show that Time-HOBI offers a promising star query performance.