gmpy adapter

Hello, all,

I have a client app that reads in many values from a numeric column,
does some heavy computations, then writes the results back to another
numeric column.

Python's decimal.Decimal is SLOOOOoooow. I'm trying to use gmpy.mpq
instead. I have the adapter for reading the values from the database
working fine:

numeric2mpq = lambda d,c: None if d is None else gmpy.mpq(d)
MPQ = psycopg2.extensions.new_type((1700,), "MPQ", numeric2mpq)
psycopg2.extensions.register_type(MPQ)

This is the adapter I'm using for the reverse (converting the mpq to a
string suitable for casting to numeric):

def mpq2numeric(mpq):
s = '%d::numeric/%d::numeric' % (mpq.numer(), mpq.denom())
return psycopg2.extensions.AsIs(s)
psycopg2.extensions.register_adapter(gmpy.mpq(0).__class__,
mpq2numeric)

While the adapter works, it seems less than optimal as it creates an
expression for the server to process, e.g:

print psycopg2.extensions.adapt(gmpy.mpq('.333'))
333::numeric/1000::numeric

Questions:

1) Is there something I'm overlooking with gmpy that could make this
much simpler?

2) What other solutions do folk use for working around pythons slow,
slow, slow Decimal?

Thanks,

Dan