Re: [sqlalchemy] How to correctly merge objects of type X or any subclass of type X into the session?

2016-02-16 Thread Mike Bayer 



On 02/16/2016 11:42 AM, Michael Naber wrote:

That's interesting. So, if I'm trying to move instances between threads,
is it recommended that I pass between threads the instance id, and then
in the receiving thread use session.query(Person).get(instance_id),
or... should I pass the instance itself (not by ID), and then use
session.merge(instance)?

My objective is that I would want to have full access to access and
modify the instance in the session of the receiving thread.


you can pass the full instance from one thread to another, and have the 
receiving thread merge() it into the receiving session.   the only thing 
you need to watch for in this case is that the receiving thread is now 
going to be handling the object you give it in a read-only sense, but if 
that object is still associated with the originating thread's Session 
then you're going to have thread-concurrent access to that session, 
which is dangerous.  So you can either synchronize the threads on the 
point at which the receiving thread is calling merge() or you can detach 
the object from the Session before giving it to the receiving thread.







Thank you,
Michael

On Tue, Feb 16, 2016 at 11:26 AM, Mike Bayer > wrote:

answered



On 02/16/2016 09:08 AM, Michael Naber wrote:

I would like to write code which can correctly merge objects of
type X
or any subclass of type X into the session. I have been doing
session.merge(X(id=??)), which works fine for merging type X,
but if the
object ID references an instance of any subclass of X, the merge
results
in the discriminator being set incorrectly. Code example here:
http://stackoverflow.com/questions/35414057

Any help much appreciated.

Regards,
Michael

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Re: [sqlalchemy] How to correctly merge objects of type X or any subclass of type X into the session?

2016-02-16 Thread Michael Naber 
That's interesting. So, if I'm trying to move instances between threads, is
it recommended that I pass between threads the instance id, and then in the
receiving thread use session.query(Person).get(instance_id), or... should I
pass the instance itself (not by ID), and then use session.merge(instance)?

My objective is that I would want to have full access to access and modify
the instance in the session of the receiving thread.

Thank you,
Michael

On Tue, Feb 16, 2016 at 11:26 AM, Mike Bayer 
wrote:

> answered
>
>
>
> On 02/16/2016 09:08 AM, Michael Naber wrote:
>
>> I would like to write code which can correctly merge objects of type X
>> or any subclass of type X into the session. I have been doing
>> session.merge(X(id=??)), which works fine for merging type X, but if the
>> object ID references an instance of any subclass of X, the merge results
>> in the discriminator being set incorrectly. Code example here:
>> http://stackoverflow.com/questions/35414057
>>
>> Any help much appreciated.
>>
>> Regards,
>> Michael
>>
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>>
>
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Re: [sqlalchemy] How to correctly merge objects of type X or any subclass of type X into the session?

2016-02-16 Thread Mike Bayer 

answered


On 02/16/2016 09:08 AM, Michael Naber wrote:

I would like to write code which can correctly merge objects of type X
or any subclass of type X into the session. I have been doing
session.merge(X(id=??)), which works fine for merging type X, but if the
object ID references an instance of any subclass of X, the merge results
in the discriminator being set incorrectly. Code example here:
http://stackoverflow.com/questions/35414057

Any help much appreciated.

Regards,
Michael

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[sqlalchemy] How to correctly merge objects of type X or any subclass of type X into the session?

2016-02-16 Thread Michael Naber 
I would like to write code which can correctly merge objects of type X or
any subclass of type X into the session. I have been doing
session.merge(X(id=??)), which works fine for merging type X, but if the
object ID references an instance of any subclass of X, the merge results in
the discriminator being set incorrectly. Code example here:
http://stackoverflow.com/questions/35414057

Any help much appreciated.

Regards,
Michael

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