Cost-based optimization of aggregation star queries on hierarchically clustered data warehouses

Aris Tsois, Nikos Karayannidis, Timos K. Sellis, Dimitri Theodoratos
2002 Design and Management of Data Warehouses  
A methodology recently proposed to improve processing of star queries on data warehouses is the clustering and indexing of fact tables using their multidimensional hierarchies [DRSN98, MRB99, KS01]. Due to this improved organization schema, processing of aggregation star queries changes dramatically creating new optimization opportunities. An important optimization technique is the so-called pre-grouping transformation. Although this transformation is expected to improve the query-processing
more » ... n in most cases, there are several cases where it is not beneficial. In this paper we attempt to apply a cost-based method for the optimal application of the pre-grouping transformation. Taking into consideration the special characteristics of our domain we identify the most suitable algorithms for the operations related to pre-grouping and derive detailed cost formulas for them. When proper statistical information is available the method can decide (1) whether or not to use the pre-grouping transformation and (2) which combination of algorithms to use for the various operations involved.
dblp:conf/dmdw/TsoisKST02 fatcat:avfxnetmfrhzzfiubf7dpjjs7y