QGIS » QGIS Application

what platform and qgis version?

tested on:
- ubuntu 10.04 + qgis trunk
- win xp + qgis 1.7.4
- win server 2003 + qgis 1.7.4
- win 7 + qgis 1.7.4

All the same behaviour

here an example of mapserver (6.4.1) mapfile not working for me:

MAP
    NAME "test_wms" 
    EXTENT 648300 5090700 677500 5116000
    UNITS meters
    MAXSIZE 10000
    IMAGECOLOR 255 255 255
    RESOLUTION 96
    CONFIG "PROJ_LIB" "/usr/local/share/proj/" 

    PROJECTION
        "init=epsg:25832" 
    END

    WEB
        METADATA
            "wms_title"                     "test_wms" 
            "wms_onlineresource"            "http://localhost/cgi-bin/mapserv?map=test_wms.map&" 
            "wms_srs"                       "EPSG:25832" 
            "wms_feature_info_mime_type"    "text/plain" 
            "wms_abstract"                  "Abstract" 
            "wms_enable_request"            "*" 
        END
        IMAGEPATH "/tmp/" 
    END

    LAYER
        NAME "polygon_layer" 
        CONNECTIONTYPE postgis
        CONNECTION "dbname=mydb host=localhost" 
        DATA "wkb_geometry FROM polygon_layer" 
        EXTENT 648300 5090700 677500 5116000
        GROUP test_wms
        TYPE POLYGON
        STATUS OFF
        SYMBOLSCALEDENOM 2000
        TEMPLATE void
        MINSCALEDENOM 50
        METADATA
            "wms_title"                     "polygon_layer" 
            "wms_enable_request"            "*" 
        END
        CLASS
            NAME "polygon layer" 
            STYLE
                WIDTH 3
                OUTLINECOLOR 255 0 255
                LINECAP butt
                PATTERN 8 4 END
            END
        END
    END

    LAYER
        NAME "line_layer" 
        CONNECTIONTYPE postgis
        CONNECTION "dbname=mydb host=localhost" 
        DATA "wkb_geometry FROM line_layer" 
        EXTENT 648300 5090700 677500 5116000
        GROUP test_wms
        TYPE LINE
        STATUS OFF
        TEMPLATE void
        SYMBOLSCALEDENOM 1000
        MINSCALEDENOM 50
        METADATA
            "wms_title"                     "line_layer" 
            "wms_enable_request"            "*" 
        END
        CLASS
            NAME "line layer" 
            STYLE
                COLOR 255 0 0
                LINECAP butt
                WIDTH 2
                PATTERN 6 6 END
            END
        END
    END

    LAYER
        NAME "point_layer" 
        CONNECTIONTYPE postgis
        CONNECTION "dbname=mydb host=localhost" 
        DATA "wkb_geometry FROM point_layer" 
        EXTENT 648300 5090700 677500 5116000
        GROUP test_wms
        TYPE POINT
        STATUS OFF
        TEMPLATE void
        SYMBOLSCALEDENOM 1000
        MINSCALEDENOM 50
        METADATA
            "wms_title"                     "point_layer" 
            "wms_enable_request"            "*" 
        END
        CLASS
            NAME "point layer" 
            STYLE
                COLOR 0 0 0
                SYMBOL "circle" 
                SIZE 8
            END
        END
    END

END

The reason is that in the GetCapabilities document that Mapserver creates the group layer is not marked as queryable. I hit the same issue yesterday when I tried to cascade WMS from Mapserver with Geoserver https://lists.osgeo.org/pipermail/mapserver-users/2016-January/078538.html.
I would say that QGIS works as supposed and the bug is on the Mapserver side.

Thanks for the explanation, I agree with you. Only a precisation: if the WMS Client queries the group layer - even if it is not marked as queryable - mapserver responds correctly with GetFeatureInfo response.

Yes, but it seems to require that every individual layer in the group is queryable. If one layer in not queryable Mapserver turns the whole group non-queryable.

Jukka Rahkonen wrote:

Yes, but it seems to require that every individual layer in the group is queryable. If one layer in not queryable Mapserver turns the whole group non-queryable.

In the Médéric's WMS example (http://geoservices.brgm.fr/geologie) if you try to open the 5 layers inside the group BSS (BSS_SEMIS_2, BSS_SEMIS_1, BSS_SEMIS_0, BSS_TOTAL_AVEC_LABEL, BSS_TOTAL_SANS_LABEL) they are all queryable. If you open the group BSS that contains those layers (id=19), it is not queryable

Giovanni Manghi wrote:

michele zanolli wrote:

Jukka Rahkonen wrote:

Yes, but it seems to require that every individual layer in the group is queryable. If one layer in not queryable Mapserver turns the whole group non-queryable.

In the Médéric's WMS example (http://geoservices.brgm.fr/geologie) if you try to open the 5 layers inside the group BSS (BSS_SEMIS_2, BSS_SEMIS_1, BSS_SEMIS_0, BSS_TOTAL_AVEC_LABEL, BSS_TOTAL_SANS_LABEL) they are all queryable. If you open the group BSS that contains those layers (id=19), it is not queryable

so it needs futher tests.

I need to clarify:

- With Mapserver group layer is never announced as queryable in the GetCapabilities
- However, if all the layers in the group are queryable, it is possible to to query the group by making a GetFeatureInfo request with &QUERY_LAYERS=group (but QGIS does not know that)
- If at least one layer in the group is not queryable then the group in not queryable either and GetFeatureInfo with &QUERY_LAYERS=group will yield an exception from Mapserver.

This behaviour makes it tricky to program a workaround on QGIS side. QGIS should check that the WMS server is Mapserver with some heuristics, and if it is, then check if all the layers in the group are queryable. If they are the group is queryble as well. Brute force approach would be just to fire GetFeatureInfo always - if layer or group is not queryable the server will tell it by sending an exception.

I think that this is not a bug in QGIS and the right place to fix the issue is on the Mapserver side.