Same answer. Each request is handled in a separate thread, so any code in a
model, controller, or view is run in a fresh environment. When you define a
table or specify callbacks in a model file, it's like it is happening for
the first time (as it only applies to the current request) -- it is not as
if a new copy of your callback function is being appended to an
ever-growing list on every request. You would only be appending the same
function twice if your code includes:
db.tt._after_update.append(myfunc)
in two separate places.
Anthony
On Thursday, July 30, 2015 at 11:01:51 AM UTC-4, Thomas Sitter wrote:
>
> Sorry I should have clarified my question.
>
> The part I'm concerned about is the use of *append* when adding the
> callback. If append is being used is there any check to make sure a
> function is not already in the list. I do not want to call the same
> callback multiple times when a record is updated.
>
> In the sourcecode _after_callback is implemented as a list and I see no
> checks to make sure the same function isn't inserted/called more than once.
> Perhaps it should be a set?
>
>
>
> On Thursday, 30 July 2015 00:50:49 UTC-4, Anthony wrote:
>>
>> auth.add_group() actually does a database insert, so you don't want to
>> keep repeating it on every request (actually, I would probably move that
>> code out of the app altogether, as it really only needs to be run once
>> ever).
>>
>> Specifying the after update callback, on the other hand, does not affect
>> the database at all -- it simply tells the DAL what to do after a database
>> update. In fact, you need this to run on every request because it is part
>> of the model definition (for the same reason you need to run the associated
>> db.define_table() on every request).
>>
>> Anthony
>>
>> On Wednesday, July 29, 2015 at 10:59:59 PM UTC-4, Thomas Sitter wrote:
>>>
>>> Hello,
>>>
>>> I'm adding an _after_update callback to my table in db.py using:
>>>
>>> def myfunc(s,f):
>>> #do stuff
>>> return False
>>>
>>> db.tt._after_update.append(myfunc)
>>>
>>> My question is whether this will continuously append this method every
>>> time a database table is modified.
>>>
>>> I'm asking because I had a similar issue when creating the initial auth
>>> users/groups in db.py. I had to wrap the code in the following logic to
>>> prevent them being added multiple times
>>>
>>> if not db().select(db.auth_user.ALL).first():
>>> group_1 = auth.add_group('group1', 'group1 employees')
>>> ...
>>>
>>>
>>> Thanks
>>>
>>
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