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Database application has shifted away from traditional business
application. Support for nontraditional application, like VLSI
CAD, decision support system, etc, are todays 'hot topics'. But
current database systems are complex monoliths that are
expensive to build and exceedinhly difficult to modify, so the
research about extensible DBMSs is getting more important. In
the research of query processing about extensible DBMSs, some
systems support the incorporation of C function made by user,
but the return object is a scalar; some paper discuss how to
customize the algorithms of operators, but most of them
concentrate on adding more operators to an existing system.
Hardly anyone has set attention to adding necessary functions
in some application. In this paper, we propose the design and
implementation of an extensible query module. We propose three
types of functions, including relation function, aggregation
function, and scalar function. Also, we support user some
keywords and system functions to custom his/her function.
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