Caching/Indexing Function Output

Hello,

I've written several functions using the SPI_ interface, some of them are to
simply ease inserting into a few tables-

ie- I wrote a function sp_host('10.0.0.1'); which returns the id of the
given
ip address from a ip_addresses table if it exists, otherwise, it inserts it,
and
returns that id. We use this to keep the logic simple when inserting new
entries
into a weblogs table-

    insert into weblogs (..., host) values (..., sp_host('10.0.0.1'));

We also use this for a dozen or so other similar tables-

My question is- is there anyway, since a call to sp_host('10.0.0.1') will
always
return the same value (the primary key/sequence value from the ip_addresses
table), to cache/index that value somehow, so anytime I ever call that same
function, with the same argument, it returns a cached/indexed value?

ie- I make an initial call to sp_host('10.0.0.1'), which returns the id
1000; the
system caches this, and stores:

function=sp_host, arg='10.0.0.1', return=1000

or

key=sp_host('10.0.0.1'), value=1000

the next time I call sp_host, with the same arg, it simply returns 1000,
instead
of actually calling the function?

clearly I don't want to do this for *all* the functions I've written, but it
would
probably speed these functions up considerably?

Thanks!

Mike Pultz
mike@mrhost.ca