[Qgis-developer] Updating field with a trigger

[Bernhard Ströbl]

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).

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.

Bernhard


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.
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