A Tool for Nesting and Clustering Large Objects
S. Dieker, R.H. Güting, and M. Rodriguez-Luaces
Praktische Informatik IV, FernUniversität Hagen
D-58084 Hagen, Germany
{stefan.dieker, gueting, miguel.rodriguez-luaces}@fernuni-hagen.de
Abstract: In implementations of non-standard database systems, large
objects are often embedded within an aggregate of different types,
i.e. a tuple. For a given size and access probability
of a large object, query performance depends on the representation
of the large object: either inlined within the aggregate or swapped out
to a separate object. Furthermore, the implementation of complex data models
often requires nested large objects, and access performance is highly
influenced by the clustering strategy followed to store the resulting tree
of large objects.
In this paper, we describe a large object extension which automatically
clusters nested large objects. A rank function is developed which
indicates the suitability of a large object being inserted into a given
cluster. We present two clustering algorithms of different run-time complexity,
both using the rank function, and a series of simulations is performed
to compare them to each other as well as to two trivial ones. One of the
algorithms proves to compute the most efficient clustering in all tests.
Keywords: large objects, clustering, type constructors,
data types, extension packages
Published: Proc. of the 12th Int. Conf. on Scientific and Statistical
Database Management (SSDBM 2000), 169-181, July 2000.