Aqua: A Fast Decision Support Systems Using Approximate Query Answers
Swarup Acharya, Phillip B. Gibbons, Viswanath Poosala · Very Large Data Bases · 1999
Aqua is a system for providing fast, approximate answers to aggregate queries, which are very common in OLAP applications. It has been designed to run on top of any commercial relational DBMS. Aqua precomputes synopses (special statistical summaries) of the original data and stores them in the DBMS. It provides approximate answers (with quality guarantees) by rewriting the queries to run on these synopses. Finally, Aqua also incrementally keeps the synopses up-to-date as the database changes.