Named Parameters In Database Functions With Sqlalchemy

I have a function in my database (Postgres) that looks like this: create function test_f(a text default '*', b text default '+') returns text as $$ select a || ' ' || b; $$ lan

Solution 1:

Thanks to the suggestion of Michael Bayer, I came up with a solution to my own question: the trick is to use SQLAlchemy's compiler, and some proper escaping:

from psycopg2.extensions import adapt as sqlescape                          
import sqlalchemy                                                           
from sqlalchemy import select                                               
from sqlalchemy.ext.compiler import compiles                                
from sqlalchemy.sql.expression import ColumnClause                          


class MyFunc(ColumnClause):                                                 
    def __init__(self, *args, **kwargs):                                    
        self.kwargs = kwargs                                                
        super().__init__(*args)                                             


@compiles(MyFunc)                                                           
def compile_myfunc(element, compiler, **kw):                                
    s = ','.join("%s:=%s" % (k, sqlescape(v)) for k, v in element.kwargs.items())
    return "%s(%s)" % (element.name, s)                                     


def call(engine, func, **kwargs):                                           
    return engine.execute(select([MyFunc(func, **kwargs)]))                 


engine = sqlalchemy.create_engine('postgresql+psycopg2://lbolla@localhost/mytest')
print(call(engine, 'test_f', a='a').scalar())                               
print(call(engine, 'test_f', b='b').scalar())