On Fri, Oct 20, 2023, at 9:50 AM, 'Tony Cosentini' via sqlalchemy wrote:
> Weird, I did try that but I can't seem to trigger it.
>
> Here's a self-contained test:
> https://gist.github.com/tonycosentini/4dee3478695d032ca67707b5e26739b6
the object was not affected in that query (that is, not mutated). if you
change the query to this:
table_one_instances = session.query(TableOne).populate_existing().all()
then the refresh event is triggered.
Im not really following what kind of bug you are trying to detect.
>
> I have the event listener set to just crash, but it never triggers.
>
> On Fri, Oct 20, 2023 at 9:20 PM Mike Bayer
> <[email protected]> wrote:
>> __
>>
>>
>> On Fri, Oct 20, 2023, at 8:08 AM, 'Tony Cosentini' via sqlalchemy wrote:
>>> Hi,
>>>
>>> Is there any way to listen for an event for when a query result gets merged
>>> into a pre-existing object in the session?
>>
>> this is the refresh event:
>>
>> https://docs.sqlalchemy.org/en/20/orm/events.html#sqlalchemy.orm.InstanceEvents.refresh
>>
>>
>>>
>>> I'm working on disabling autoflush for some of our codebase (mostly to cut
>>> down on queries on a high QPS path), but before doing that I want to write
>>> a utility to detect when we read data that was flushed via autoflush to cut
>>> down on any potential bugs.
>>>
>>> What I'd like to do is this (while autoflush is still enabled):
>>>
>>> table_one = TableOne(name='test')
>>> session.add(table_one) # Track this object as pending a flush via the
>>> before_* listeners, this is working as expected.
>>>
>>> table_two_instances = session.query(TableTwo).all() # All good, doesn't do
>>> anything with the table_one instance created earlier
>>>
>>> table_one_instances = session.query(TableOne).all() # I would like to log a
>>> warning here as the results of this query depend on a flush happening. What
>>> I'm hoping to do is detect that one of the rows coming back is the same
>>> object that was flagged earlier, but I can't see to find the correct event
>>> to use.
>>
>> you probably want to also use refresh_flush also, which will be invoked for
>> column defaults that are populated on the object
>>
>> https://docs.sqlalchemy.org/en/20/orm/events.html#sqlalchemy.orm.InstanceEvents.refresh_flush
>>
>>
>>
>>
>>>
>>> Is this possible? I can't seem to find the appropriate event that would
>>> trigger when the results from the .all() query get merged back in with the
>>> existing objects in the session.
>>
>> that's the refresh event
>>
>>
>>
>>
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>
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