How do I use a filter on an uncached WFS layer in QGIS?

Question

I am trying to create a filter to show only specific features based on an attribute query within a WFS using QGIS. This works fine when using the standard WFS loader and creating a filter (based on the type "attribute"='value'). However this only works when the features are cached.

I want to be able to use a filter like this for an uncached WFS layer. Does anyone have any idea how to do this?

Example using a BGS public WFS.

A standard cached query would look like this:

http://ogc.bgs.ac.uk/cgi-bin/BGS_Bedrock_and_Superficial_Geology/wms?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=GBR_BGS_625k_SLS&SRSNAME=CRS:84&FILTER=<ogc:Filter xmlns:ogc="http://www.opengis.net/ogc">
 <ogc:PropertyIsEqualTo>
  <ogc:PropertyName>LEX_ROCK_D</ogc:PropertyName>
  <ogc:Literal>PEAT</ogc:Literal>
 </ogc:PropertyIsEqualTo>
</ogc:Filter>

When I untick the cached option, the layer source is as follows:

http://ogc.bgs.ac.uk/cgi-bin/BGS_Bedrock_and_Superficial_Geology/wms?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=GBR_BGS_625k_SLS&SRSNAME=CRS:84&BBOX=-3.4085901736001083,57.05755199511002473,-2.94851240830698069,57.42328922738386154&FILTER=<ogc:Filter xmlns:ogc="http://www.opengis.net/ogc">
 <ogc:PropertyIsEqualTo>
  <ogc:PropertyName>LEX_ROCK_D</ogc:PropertyName>
  <ogc:Literal>PEAT</ogc:Literal>
 </ogc:PropertyIsEqualTo>
</ogc:Filter>

The main difference is the bounding box. What happens with the second layer definition is that the layer loads but has no features within it.

I am able to create a GeoServer layer within my WFS that meets this query, but I am trying to find a way that users will be able to replicate without intervention at the GeoServer end.

Answer 1

The problem is that the WFS provider of QGIS appends BBOX element to the main URL for unchached features request and if a filter exists it produces:

msWFSGetFeature(): WFS server error. BBOX parameter and FILTER parameter are mutually exclusive in GetFeature.

So to solve the problem the BBOX element should be included in the FILTER element to get a request like:

<ogc:Filter xmlns:ogc="http://www.opengis.net/ogc">
 <ogc:PropertyIsEqualTo>
  <ogc:PropertyName>batimetria</ogc:PropertyName>
  <ogc:Literal>200</ogc:Literal>
 </ogc:PropertyIsEqualTo>
 <gml:Box>
  <gml:coordinates>0.49585,34.1375 23.50415,49.3625</gml:coordinates>
 </gml:Box>
</ogc:Filter>

In current version it is not possible, you could file a ticket in the bug tracker