.sh 1 "CONCLUSION" 6
.pp
It will be interesting to run further tests on the optimizer once
it has been fully integrated with the rest of POSTGRES.
Among the issues of interest are:
.ip "\(bu"
whether writing the optimizer in LISP is a performance concern
.ip "\(bu"
whether the optimizer \fIactually\fR selects true optimal plans
.ip "\(bu"
whether the optimizer really works with \fIall\fR user-defined types, operators,
and access methods
.ip "\(bu"
whether the current algorithm for optimizing nested-attribute queries is
\*(lqgood enough.\*(rq
.lp
.pp
Clearly, further validation of the POSTGRES optimizer is necessary to
examine the more subtle issues raised by these questions.
However, the preliminary work described in this report has at least
illustrated the feasibility of many important ideas.
Most significant of these are the concepts introduced to support 
optimization of extendibile objects in a database system.
