[Qgis-developer] Change the query of a query layer (postgis)

[Olivier Dalang]

Hi Enrico,

Hmm I didn't think of that, thanks for the idea ! But I can't use it since
I may have several user at once.

Best,

Olivier

2015-06-17 16:03 GMT+02:00 enricofer <enricofer at gmail.com>:

> Hi Olivier,
> In your case, I think that the best way to do this is to create a view
> from the sql query and load it as layer, than, when qslider changes, change
> the view definition with "ALTER VIEW"  and reload the layer.
>
> Regards,
>
> Enrico Ferreguti
>
> Il giorno 17/giu/2015, alle ore 14:29, olivier [via OSGeo.org] <[hidden
> email] <http:///user/SendEmail.jtp?type=node&node=5211452&i=0>> ha
> scritto:
>
> Hi !
>
> Is it possible to change the query of a postgis query layer in python
> without reloading the project ?
>
> The goal is to have a parameter in my query that I'd be able to change
> with a slider.
>
> I tried the QgsVectorLayer.setDataSource() method, but it makes QGis crash.
> I tried the workaround described here (
> http://gis.stackexchange.com/questions/62610/changing-data-source-of-layer-in-qgis
> ), writing and reading the XML file, but it also makes QGis crash.
>
> If not possible, is there a serious limitation behind this, or is the
> feature just missing/bugged ?
>
> Example :
>
> I have this query loaded as a layer:
>
> "SELECT id, name, ST_Buffer(geom,25) as geom FROM my_table"
>
> But I want to be able to change the hardcoded buffer from 25 to some value
> from a QSlider.
>
> Thanks!
>
> Olivier
>
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