[Qgis-developer] Updating field with a trigger

[Bernhard Ströbl]

Hi Yves,

Am 10.09.2015 um 09:27 schrieb Yves Jacolin:
> Hello,
>
> On Thursday, September 10, 2015 8:50:24 Bernhard Ströbl wrote:
>> Hi Yves,
>>
>> I have only experience with PostgreSQL but I assume that sqlite behaves
>> similar. If you edit a feature in QGIS your layer is in edit mode
>> (allowing for undo/redo). Changes are committed only when you click on
>> the respective button. This results in an update statement sent to your
>> db which then calls your trigger. Thus field#2 is not changed when you
>> change #1 _in QGIS_. In order to have such behaviour AFAIK you would
>> have to do it in Python (which would be totally independent from the db
>> trigger then).
> Thanks for confirmation.
>
>> Apart from that if
>> field#2 = field#1 + x
>> then field#2 is totally redundant. You could either create a view
>> containing this field or create a virtual field in QGIS.
> I just simplified for the test case. This is more complicated but was not
> useful to give such details ;)


still this should be considered an option to show the resulting value to 
the user instead of having it in a field of its own.

>
> Thanks again Bernhard!

You're welcome

Bernhard

>
> Y.
>>
>> Am 09.09.2015 um 13:41 schrieb Yves Jacolin:
>>> Hello,
>>>
>>> I have a small project with a sqlite db. There is a layer with a trigger
>>> on a field #1 to calculate an addition and put the result in another
>>> field (#2).
>>>
>>> When I edit the initial field #1, the second field #2 is not updated in
>>> the
>>> form. I need to close the form and open it again to see the result.
>>>
>>> Do you think this is a known limitation or a bug?
>>>
>>> My point of view is that it is a limitation, as QGIS don't know that a
>>> trigger can change a value in the same feature server side.
>>>
>>> I don't know if QGIS should or could get an update of the data server side
>>> before display the form content.
>>>
>>> In case there is no such plan, do you think we can add some logic in a
>>> python script to force the form update (I can ask to Arnaud next week on
>>> this topic).
>>>
>>> Thanks,
>>>
>>> Y.


__________ Information from ESET Mail Security, version of virus signature database 12230 (20150910) __________

The message was checked by ESET Mail Security.
http://www.eset.com