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

[enricofer]

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] <
ml-node+s1560n5211424h13 at n6.nabble.com> 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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