Query optimization by using derivability in a data warehouse environment
Jens Albrecht, Wolfgang Hümmer, Wolfgang Lehner, Lutz Schlesinger · 2000
Materialized summary tables and cached query results are frequently used for the optimization of aggregate queries in a data warehouse.Query rewriting techniques are incorporated into database systems to use those materialized views and thus avoid the access of the possibly huge raw data.A rewriting is only possible if the query is derivable from these views.Several approaches can be found in the literature to check the derivability and find query rewritings.The specific application scenario of a data warehouse with its multidimensional perspective allows the consideration of much more semantic information, e.g.structural dependencies within the dimension hierarchies and different characteristics of measures.The motivation of this article is to use this information to present conditions for derivability in a large number of relevant cases which go beyond previous approaches.