On Dec 18, 2010, at 5:32 AM, drakkan wrote:
> Hi,
>
> inspecting the gc I see a sqlalchemy memory leak in my application,
> here is the output from the gc:
>
> <class 'sqlalchemy.engine.base.Connection'>: 2 -> 3 (+1)
> <class 'sqlalchemy.engine.base.RootTransaction'>: 2 -> 3 (+1)
> <class 'sqlalchemy.util.LRUCache'>: 1 -> 2 (+1)
> <class 'sqlalchemy.util.PopulateDict'>: 2 -> 3 (+1)
> <type 'tuple'>: 5987 -> 5990 (+3)
> <class 'sqlalchemy.sql.expression._BindParamClause'>: 73 -> 80 (+7)
> <type 'dict'>: 8943 -> 8954 (+11)
> <class 'sqlalchemy.sql.expression.Insert'>: 1 -> 2 (+1)
> <class 'sqlalchemy.util.OrderedDict'>: 180 -> 181 (+1)
> <type 'instancemethod'>: 490 -> 487 (-3)
> <class 'sqlalchemy.dialects.sqlite.base.SQLiteCompiler'>: 2 -> 3 (+1)
> <type 'collections.defaultdict'>: 34 -> 35 (+1)
> <type 'weakref'>: 3830 -> 3831 (+1)
> <type 'list'>: 2953 -> 2963 (+10)
>
> every time I make some database object a reference is added to
> sqlalchemy objects and never released. I'm sure the problem is my
> application and not sa, however I would like to know how to force
> sqlalchemy to delete objects references.
>
> I'm using these function to query gc:
>
> def gcHistogram(self):
> import gc
> result = {}
> for o in gc.get_objects():
> t = type(o)
> count = result.get(t, 0)
> result[t] = count + 1
> print len(result)
> return result
>
> def diffHists(self,h1, h2):
> for k in h1:
> if k in h2:
> if h1[k] != h2[k]:
> print "%s: %d -> %d (%s%d)" % (
> k, h1[k], h2[k], h2[k]
> > h1[k] and "+" or "", h2[k] - h1[k])
SQLA doesn't maintain strong references to anything at the module level. The
objects you have above appear to be related to the "compiled cache" used by an
individual mapper. This is an LRU-enabled dictionary that holds onto Insert
constructs and their compiled form up to approximately 100 elements. The
dictionary is associated with a mapper, which in turn is associated with your
mapped class. If you dereference your mapped class (and all instances of that
class), the mapper and the LRU cache will be gone. You can also say
mapper._compiled_cache.clear() which will probably remove the
Insert/SQLiteCompiler objects above.
As for Sessions, if you close(), commit(), rollback(), or expire_all() the
session object, all user objects inside are weakly referenced by the session
(though related objects will have strong references to each other).
>
> thanks
> Nicola
>
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