[Qgis-developer] Updating field with a trigger

[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 ;)

Thanks again 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.
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