Storing computed values

Greetings.

I have a question regarding storing computed values. Essentially, it's
a question about caching, and I'm willing to implement a cache on the
client side or using pg_memcache, but I wonder if I can do this in a
PostgreSQL table, instead?

The background is that I'm using PostGIS to store thousands of points
across the globe. Once in a while, I want to connect a subset of these
points using an algorithm I have in a PL/Perl procedure. Depending on
where the endpoints are located, this algorithm takes between 10 ms and
40 ms to run for each pair of points. Hundreds of these points are
connected and then displayed over the web, which, essentially, takes a
really long time. Some connections are calculated very frequently, and
some connections will probably never be calculated, though it's
difficult to determine which connections fit those descriptions.

The locations of these points sometimes change, and, relatively
infrequently, new points are added. Even more infrequently, some points
are deleted.

I would like to have a table that contains a connection for each
distinct pair of points (point1 to point2 is the same as point2 to
point1). This table would then be automatically updated every time a
modification is made to the reference table. If my calculation is
correct, the new table would contain 3,654,456 rows using the current
data set.

I realize I could use a TRIGGER to keep the connections table fresh, and
perhaps that's also a solution.

But, really, I'm just wondering if PostgreSQL has some automated,
built-in facility for situations like this?

Thanks.

Colin