this is all about whatever you've done specifically. If you have the Session
instance still around, where my_session.bind still points to your Engine, then
that Engine is still in memory - you're holding a reference to it. Similarly,
if you've assigned an event to the Session class whose callable refers to the
Engine in question, then the Engine is still referenced as well, such as:
def make_evt(engine):
@event.listens_for(Session, "before_flush")
def go(session, ctx):
# do something with engine
make_evt(my_engine)
the above code will associate "my_engine" with a class-level Session listener
and cannot be dereferenced without unloading all of sqlalchemy.orm.
dispose() and NullPool have *nothing to do* with the Engine itself, only the
connections inside the pool contained within. Your Engine will remain present
as long as its reachable via references, just like any other Python object.
On Jan 10, 2013, at 11:55 PM, Anoop K wrote:
> I tried session.bind.dispose() and NullPool. But engine is still not cleared.
> It still seems to have some reference from SessionEventsDispatch =>
> sqlalchemy.event._DispatchDescriptor.
>
>
>
> On Friday, 11 January 2013 05:24:19 UTC+5:30, Michael Bayer wrote:
>
> On Jan 10, 2013, at 8:25 AM, Anoop K wrote:
>
>> It seems engine created using create_engine is not freed after cleanup of a
>> session. Object graph indicates that event.listen for pool is holding
>> reference to engine even after session is garbage collected.
>> What is the right way/api to delete an engine ?
>>
>> UseCase
>> As there are lot of databases in multiple boxes whose ip/user/password can
>> change I would like to destroy session and engine after use. Cost of
>> creating/closing connection can be ignored for my use case.
>>
>>
>
> engines can be disposed using engine.dispose() to close connections referred
> to by the pool, and then removing all references to that engine.
>
> if you aren't concerned about connection pooling (which seems to be the case
> here if you're looking to dispose engines regularly) then just use NullPool
> with create_engine(..., pool_class=NullPool). Then dispose() isn't really
> needed, just lose references to the engine.
>
>
>
>
>
>
>>
>>
>>
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>
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