On Jan 19, 2006, at 8:21 PM, Michael Bayer wrote:
OK, that was a bug where it breaks down a save dependency into a
hierarchical graph of smaller dependencies, when you have a circular
mapper going...it was forgetting about all the other dependent
operations on the original save dependency. my three current tests
for self-referring mappers didnt take this case into account....so
your test is working now if you update.
thanks mike; things seem to be working
for my actual work code.
the dependency processing is still pretty
opaque to me, but i did notice that in
topological.py(L79-81) you have:
if t[0] is t[1]:
nodes[t[0]].circular = True
continue
i was trying to understand the implications
of this.
as a test i looked into trying to create
a 2-loop in the code below, but failed
because FKs require the referent to already
exist. the followup question to this is:
do you imagine ever allowing the creation
of such relations via sqlalchemy?
i was still curious as to what would happen
if i manually created the table definitions
and commented out the .create()s - in that
case i got a:
".../mapping/topological.py", line 96, in sort
raise "Circular dependency detected " + repr(edges) + repr(queue)
Circular dependency detected {Mapper|C2|t2 (idself=1077381996):
{Mapper|C1|t1 (idself=1077381964): True}, Mapper|C1|t1
(idself=1077381964): {Mapper|C2|t2 (idself=1077381996): True}}[]
which makes sense, since the cycle won't get
caught by the 't[0] is t[1]' check.
nevertheless, i also wonder if this is something
that you expect to support in the future?
sorry to be bringing up less common use-cases,
but sqlalchemy gives me the hope of leveraging
these features through python.
thanks,
daishi
---
import sqlalchemy as rdb
engine = rdb.create_engine('sqlite://', echo=True)
t1 = rdb.Table(
't1', engine,
rdb.Column('id', rdb.Integer, primary_key=True),
rdb.Column('t2_id', rdb.Integer, rdb.ForeignKey('t2.id')),
)
t1.create()
class C1(object):
pass
m1 = rdb.mapper(C1, t1)
t2 = rdb.Table(
't2', engine,
rdb.Column('id', rdb.Integer, primary_key=True),
rdb.Column('t1_id', rdb.Integer, rdb.ForeignKey(t1.c.id)),
)
t2.create()
class C2(object):
pass
m2 = rdb.mapper(C2, t2)
m1.add_property('t2', rdb.relation(m2))
m2.add_property('t1', rdb.relation(m1))
a1 = C1()
a2 = C2()
a1.t2 = a2
a2.t1 = a1
rdb.objectstore.commit()
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