Ok I figured out the cause, but not the solution. I am using a mutable type
for hstore columns. I have a UserDefinedType for Hstore that just passes
everything through to psycopg2's hstore type:
class HStore(UserDefinedType):
""" SQLAlchemy type that passes through values to be handled by a
psycopg2
extension type.
"""
type_name = 'HSTORE'
def get_col_spec(self):
return self.type_name
def bind_processor(self, dialect):
return None
def result_processor(self, dialect, coltype):
return None
def is_mutable(self):
return True
def copy_value(self, value):
return copy.copy(value)
I used the MutationDict
from http://docs.sqlalchemy.org/en/rel_0_7/orm/extensions/mutable.html :
class MutationDict(Mutable, dict):
@classmethod
def coerce(cls, key, value):
"Convert plain dictionaries to MutationDict."
if not isinstance(value, MutationDict):
if isinstance(value, dict):
return MutationDict(value)
# this call will raise ValueError
return Mutable.coerce(key, value)
else:
return value
def __setitem__(self, key, value):
"Detect dictionary set events and emit change events."
dict.__setitem__(self, key, value)
self.changed()
def __delitem__(self, key):
"Detect dictionary del events and emit change events."
dict.__delitem__(self, key)
self.changed()
The column definition I use is:
some_attrs = Column(MutationDict.as_mutable(HStore))
Then in the actual transaction I am copying one object with that column
definition to another object with the same definition:
newobject.some_attrs = other_object.some_attrs
If I comment out that line there is only a single flush at the commit time.
It looks correct according to the examples I have seen, but if you know why
it keeps setting them as dirty please let me know.
On Tuesday, December 4, 2012 3:16:24 PM UTC-5, Michael Bayer wrote:
>
>
> On Dec 4, 2012, at 3:04 PM, Jason wrote:
>
> After upgrading to SQLAlchemy 0.7.9 I know receive an error "FlushError:
> Over 100 subsequent flushes have occurred within session.commit() - is an
> after_flush() hook creating new objects?" which is was introduced by
> http://docs.sqlalchemy.org/en/latest/changelog/changelog_07.html#change-75a53327aac5791fe98ec087706a2821in
> the changelog.
>
> I don't have any after_flush event handlers. I do have a before_flush
> event handler that changes the state of a related object, but that doesn't
> sound like what the error is talking about.
>
> How can I debug this further? I am doing this within a Pyramid
> application, so I am somewhat removed from the commit logic.
>
>
> this error traps the condition that dirty state remains in the Session
> after a flush has completed. This is possible if an after_flush hook has
> added new state, or perhaps also if a mapper.after_update/after_insert etc
> hook, or even a before_update/before_insert has modified the flush plan,
> which is not appropriate in any case.
>
> the best way is to actually create an after_flush() hook with a
> "pdb.set_trace()" in it; in there, you'd just look at session.new,
> session.dirty, and session.deleted to ensure that they are empty.
>
>
>
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