Ralf Hartmut Güting, Thomas Behr, Victor
Teixeira de Almeida, Zhiming Ding,
Frank Hoffmann, and Markus Spiekermann
LG Datenbanksysteme für neue Anwendungen, FB
Informatik,
Fernuniversität Hagen, D-58084
Hagen, Germany
Abstract: We describe SECONDO, an extensible DBMS platform
suitable for building research prototypes and for teaching architecture
and implementation of database systems. It does not have a fixed data
model, but is open for implementation of new models. SECONDO consists
of three major components which can be used together or independently:
(i) the kernel, which offers query processing over a set of implemented
algebras, each offering some type constructors and operators, (ii) the
optimizer, which implements the essential part of an SQL-like language,
and (iii) the graphical user interface which is extensible by viewers
for new data types and which provides a sophisticated viewer for
spatial and spatio-temporal (moving) objects. Examples of algebras
implemented in SECONDO are relations, spatial data types, R-trees, or
midi objects (music files), each with suitable operations. The kernel
is extensible by algebras, the optimizer by optimization rules and cost
functions, and the GUI by viewers and display functions.
A highlight of the description is a new algorithm for conjunctive query optimization which is remarkably simple, yet performs very well. We also emphasize a technique for selectivity estimation suitable for an extensible environment with complex algebras for non-standard data types.
Keywords: SECONDO, algebra modules, abstract data types,
extensibility, query optimization, predicate order graph, selectivity
estimation, sampling