[mapserver-users] How to set queryable=1 for a GROUP layer?

[Rahkonen Jukka (MML)]

Hi,

It seems the for Mapserver the group is queryable if all the layers in the group are queryable. Having one non-queryable layer in the group makes the whole group non-queryable. Geoserver used to do the same but now it does the opposite: if at least one layer in the group is queryable then the group is as well.
https://osgeo-org.atlassian.net/browse/GEOS-7293

If user makes GetFeatureInfo request for such mixed layer Geoserver is sending results from the queryable layers without sending exceptions about non-queryable layers. This is very user and admin friendly behavior but probably difficult to implement in Mapserver. Perhaps we could still get the queryable attribute? Logic should correspond with the current implementation: if every layer in the group and in the subgroups is queryable, set queryable="1", otherwise set queryable="0".

There seems to be a related QGIS issue https://hub.qgis.org/issues/5602.

-Jukka Rahkonen-

Lime, Steve D wrote:


Looking at mapwms.c it doesn't look like it. The code that outputs basic groups just outputs a plain <Layer> tag (L3345) with no attributes. It does look like that, at least for simple groups, it could be possible to do what you're asking by adding a private isGroupQueryable() function that would call msIsLayerQueryable() whenever a layer's group name matches the target and would return true accordingly. Not sure how that would work with subgroup support though.

Steve

From: mapserver-users [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Rahkonen Jukka (MML)
Sent: Monday, January 04, 2016 9:44 AM
To: Mapserver-Users (mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>) <mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>>
Subject: [mapserver-users] How to set queryable=1 for a GROUP layer?

Hi,

I have a layer group, let's say "group_1", where all the sub-layers are queryable.  The group layer is also effectively queryable and GetFeatureInfo works if I use &QUERY_LAYERS=group_1. The problem is that the group layer is not announced announced as queryable in the GetCapabilities

<Layer>
<Name> group_1</Name>
<Title> group_1</Title>
...
       <Layer queryable="1" opaque="0" cascaded="0">
       <Name> sub_layer</Name>
    ....


I would like to see it as:
<Layer queryable="1">
<Name> group_1</Name>
<Title> group_1</Title>
....
          <Layer queryable="1" opaque="0" cascaded="0">
          <Name> sub_layer</Name>
          ....


Without queryable attribute I can't make GetFeatureInfo to work when I am cascading it with Geoserver. By reading the WMS 1.1.1 standard I feel that GeoServer is behaving as it is supposed to work: if the layer is not announced to be queryable then it is not queryable. I can't find any mention in the WMS standard that a group layer should behave in a different way than the normal layers.

7.1.4.6 Layer Attributes
A <Layer> may have zero or more of the following XML attributes: queryable, cascaded,
opaque, noSubsets, fixedWidth, fixedHeight. All of these attributes are optional and
default to 0

7.1.4.6.1 Queryable layers
A Layer is said to be "queryable" if the server supports the GetFeatureInfo operation on
that Layer. A server may support GetFeatureInfo on some of its layers but not on all. A
server shall issue a Service Exception (code="LayerNotQueryable") if GetFeatureInfo is
requested on a Layer that is not queryable.

Is there any way to add the queryable="1" attribute to a layer group?

-Jukka Rahkonen-

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