[mapserver-users] Selecting data from multiple OGR layers

[Iljya Kalai]

Hi everyone,

I'm trying to select data from multiple OGR layers and style them based on
the source layer, as well as some attributes that are not common to all
layers.

I discovered the UNION layer
<https://mapserver.org/mapfile/union.html#union> which seems to be the
answer. According to the documentation
<https://mapserver.org/mapfile/union.html#union> the source layer name
should be in the [Combine_SourceLayerName] attribute. However, I get this
error when I try to use it:

   msOGRLayerInitItemInfo(): OGR error. Invalid Field name:
Combine_SourceLayerName in layer `LAYER1'

 (I also tried [Union:SourceLayerName] which I found in the mapunion.c code
<https://github.com/MapServer/MapServer/blob/0f7bbf67ce7c6fec0feaa0b33033daf02e406b9b/mapunion.c#L39>,
but that gives the same error.)

Map file snippet:

LAYER
    NAME "U"
    STATUS DEFAULT
    CONNECTIONTYPE UNION
    CONNECTION "LAYER1,LAYER2"
    CLASS
       NAME "C1"
       EXPRESSION ("[Combine_SourceLayerName]" = "LAYER1")
       ...

Any ideas?

Thanks!
Iljya
P.S I'm new here!
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