> > is it errorneus to explicitly put the (correct) joins even if they
> > could be figured out by SA?
> its not. but made your code that much harder to read
well, this case does require them :-(
> > which has a way to interpret python functions into Expr-trees, which
> > then can be translated (read code-generation) into whatever, like text
> > or sql-alchemy column expressions.
> are you using AST for this at least ? no need to reinvent the
> wheel....
AST... i don't parse it, python parses it. i just replace .__eq__()
with something else.
The funny thing is, the python compiled code of some expression can be
reinterpreted in diff.ways,
e.g. def myfunc(x,y): return x>100 && y.startswith('big')
..........
myfunc( 23, "big_balls_of_fire") - will eval the func yielding
true/false, while
myfunc( Var('x'), Var('y')) - will build you an expression (procided
Var()s have operators etc defined). And even give errors - not any
syntax will fit your new semantix.
of course, theoretically, there is some AST, and some grammar, but it's
sort-a virtual...
> > It's all like using the python to build _your_ syntax tree made of your
> > objects, and then use the objects - or some visitor - to do
> > code-generation/ interpretation.
> sounds awfully generic, when i could just write a little AST visitor...
Each time a new grammar and AST and new visitor? and teach users to
that new grammar? and testsuite preventing the huns into rome? mmh. i
did that. couple of "languages" per year...
Users (be them end-customers or the other-team) know their semantix
pretty well and they can cope with just about any _sensible_ easy
grammar as far as it speaks in their "lingo".
oh well. my choice is - no more grammars (lowlevel) - if i can avoid
them.
> > As i said, think of activemapper that also does inheritance and
> > queries, provided just a few hints of how user exactly wants it done.
> as far as querying, im guessing you
> are looking for an object-query-language (which is what all the "pure
> ORM" types seem to be desiring...but strangely they never get....)
not at all. SQL, OQL and probably all them *QL frighten me. Too
extreme. Looks like academical creation with little touch to mortal
people. i am targeting what u have with columns, but applied directly
to object attributes, and used more for filtering, than real
calculations.
Practical stuff, as u said - whatever we can do, now.
> > So, back to the question: inheritance and referencing together?
> im in the business of maintaining and developing
> SQLAlchemy, and if theres a bug which you can illustrate with a
> *simple* test case of around 50 lines or less, ill fix the bug,
110. can't make it less ;-)
can?
and it is about A=Employee and B=Manager, and all Employees having a
manager.
http://linuxteam.sistechnology.com/orm/sa_B_inh_A_A_ref_AB2.py
usage:
1) $ python sa_B_inh_A_A_ref_AB2.py Alink=Manager
or
2) $ python sa_B_inh_A_A_ref_AB2.py Alink=Empluyee
same 2 errors.
if of any help, i've found that if no manager (reference) is being ever
assigned, then case 1 does not crash.
-------------
from sqlalchemy import *
#table_inheritance, polymorphic
def case( Alink='Manager' ):
class Employee( object):
name = '<notset>'
def __str__(me):
return ' '.join( [me.__class__.__name__, str(me.id),
str(me.name), getattr( me.manager, 'name', '<none>') ])
class Manager( Employee ):
bonus = '<notset>'
def __str__(me):
return Employee.__str__(me) + ' ' + str(me.bonus)
db = create_engine( 'sqlite:///:memory:')
meta = BoundMetaData( db)
meta.engine.echo = 0
class tables: pass
tables.Employee = Table('Employee', meta,
Column('id', Integer, primary_key=True),
Column('name', String, ),
Column('atype', String),
Column('manager_id', Integer,
ForeignKey( Alink+'.id',
use_alter=True, name='whatever1'
)
)
)
tables.Manager = Table('Manager', meta,
Column('bonus', String, ),
Column('id', Integer,
ForeignKey( 'Employee.id'),
primary_key=True,
),
)
meta.create_all()
ajoin = {
'Employee': tables.Employee.select( tables.Employee.c.atype ==
'Employee'),
'Manager': join( tables.Employee, tables.Manager,
tables.Manager.c.id ==tables.Employee.c.id),
}
Ajoin = polymorphic_union( ajoin, None )
mA = mapper( Employee, tables.Employee,
select_table=Ajoin, polymorphic_on=Ajoin.c.atype,
polymorphic_identity='Employee'
)
mA.add_property( 'manager',
relation( Alink == 'Employee' and Employee or Manager,
primaryjoin=
tables.Employee.c.manager_id==(Alink=='Employee' and tables.Employee or
tables.Manager).c.id,
lazy=True, uselist=False, post_update=True
)
)
mB = mapper( Manager, tables.Manager,
polymorphic_identity='Manager',
inherits = mA,
inherit_condition = (tables.Employee.c.id ==
tables.Manager.c.id),
)
#populate
session = create_session()
a = Employee()
a.name = 'Dilberto'
b = Manager()
b.name = 'Boss'
b.bonus = 'big'
a.manager = (Alink == 'Employee' and a or b)
session.save(a)
session.save(b)
session.flush()
print a
print b
print list( tables.Employee.select().execute() )
print list( tables.Manager.select().execute() )
def test( klas, xid, xstr):
one = session.query( klas).get_by_id( xid)
x = str(one)
r = 'single %(x)s ; expect: %(xstr)s' % locals()
print '>>>>>', r
assert x == xstr, r
all = session.query( klas).select()
x = '; '.join( str(z) for z in all )
r = 'multiple %(x)s ; expect[0]: %(xstr)s' % locals()
print '>>>>>', r
assert len(all) >= 1, 'size? '+ r
assert str(all[0]) == xstr, r
test( a.__class__, a.id, str(a))
test( b.__class__, b.id, str(b))
import sys
kargs = dict( kv.split('=') for kv in sys.argv[1:])
case( **kargs)
==============
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