enter search term and/or author name
Large amounts of (often valuable) information are stored in web-accessible text databases. “Metasearchers” provide unified interfaces to query multiple such databases at once. For efficiency, metasearchers rely on succinct statistical...
In an uncertain database, every object o is associated with a probability density function, which describes the likelihood that o appears at each position in a multidimensional workspace. This article studies two types of range...
Multi-resolution bitmap indexes for scientific data
Rishi Rakesh Sinha, Marianne Winslett
Article No.: 16
The unique characteristics of scientific data and queries cause traditional indexing techniques to perform poorly on scientific workloads, occupy excessive space, or both. Refinements of bitmap indexes have been proposed previously as a solution...
Improving hash join performance through prefetching
Shimin Chen, Anastassia Ailamaki, Phillip B. Gibbons, Todd C. Mowry
Article No.: 17
Hash join algorithms suffer from extensive CPU cache stalls. This article shows that the standard hash join algorithm for disk-oriented databases (i.e. GRACE) spends over 80% of its user time stalled on CPU cache misses, and explores the...
SQL query optimization through nested relational algebra
Bin Cao, Antonio Badia
Article No.: 18
Most research work on optimization of nested queries focuses on aggregate subqueries. In this article, we show that existing approaches are not adequate for nonaggregate subqueries, especially for those having multiple subqueries and certain...
A top-k query combines different rankings of the same set of objects and returns the k objects with the highest combined score according to an aggregate function. We bring to light some key observations, which impose two phases that...