I'm using MySQL and sometimes SQLite as the backend database. Both
databases let me add user-defined functions. I've made a set of UDFs
specific to my problem domain, which is chemsitry.
How do I call them from a database query? Currently I'm using a raw()
call, which made for some rather ugly SQL construction.
Ideally I would like something like
q = (models.Q(title__icontains="test") &
models.Q(structure_smiles = smartsmatch(smarts="[C;!H0]"))
-or-
q = (models.Q(title__icontains="test") &
models.Q(structure_smiles__smartsmatch = "[C;!H0]"))
which would get mapped to
title LIKE 'test' AND structure_id = structure.id AND
oe_matches(structure.smiles, "[C;!H0]")
Of the two forms I gave, I prefer the first since I could see the
implementation being something simple like:
class smartsmatch(object):
def __init__(self, smarts):
self.smarts = smarts
def as_sql(self, column):
return ("oe_matches(%s, %s)", (column, smarts))
I looked but found nothing in the documentation or on the way for how
to access user-defined function in Django except through the raw()
interface.
Andrew Dalke
da...@dalkescientific.com
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