<meta http-equiv="content-type" content="text/html; charset=utf-8"><div>Hi Olivier,</div><div>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, <span style="background-color:rgba(255,255,255,0)">when qslider changes, </span>change the view definition with "ALTER VIEW" and reload the layer.</div><div><br></div><div>Regards,</div><div><br></div><div>Enrico Ferreguti<br></div><div><br>Il giorno 17/giu/2015, alle ore 14:29, olivier [via <a href="http://OSGeo.org" target="_top" rel="nofollow" link="external">OSGeo.org</a>] <<a href="/user/SendEmail.jtp?type=node&node=5211452&i=0" target="_top" rel="nofollow" link="external">[hidden email]</a>> ha scritto:<br><br></div><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' type="cite"><div>
<p dir="ltr">Hi !</p>
<p dir="ltr">Is it possible to change the query of a postgis query layer in python without reloading the project ?</p>
<p dir="ltr">The goal is to have a parameter in my query that I'd be able to change with a slider.</p>
<p dir="ltr">I tried the QgsVectorLayer.setDataSource() method, but it makes QGis crash.<br>
I tried the workaround described here (<a href="http://gis.stackexchange.com/questions/62610/changing-data-source-of-layer-in-qgis" target="_top" rel="nofollow" link="external"> http://gis.stackexchange.com/questions/62610/changing-data-source-of-layer-in-qgis</a> ), writing and reading the XML file, but it also makes QGis crash.</p>
<p dir="ltr">If not possible, is there a serious limitation behind this, or is the feature just missing/bugged ?<br><br></p>
<p dir="ltr">Example :</p>
<p dir="ltr">I have this query loaded as a layer:</p>
<p dir="ltr">"SELECT id, name, ST_Buffer(geom,25) as geom FROM my_table"</p>
<p dir="ltr">But I want to be able to change the hardcoded buffer from 25 to some value from a QSlider.<br><br></p>
<p dir="ltr">Thanks!</p>
<p dir="ltr">Olivier </p>
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