[MapServer-users] FlatGeobuf as output format

[Benedek Petrovicz]

That " ows_geomtype" actually solved my problem.
Thank you!

The reason I wrote that the promote_to_multi option won't help me is
exactly because the layer was still telling GDAL that it was a polygon
layer.
It was what I thought, that GDAL is capable of doing the conversion, it
just didn't get the correct layer type info.

Thanks again!

On Thu, Jun 22, 2023 at 10:44 AM Rahkonen Jukka <
jukka.rahkonen at maanmittauslaitos.fi> wrote:

> Hi,
>
>
>
> GDAL gives typically that kind of multipolygon error when the driver tries
> to insert a multipolygon into a layer that is created to accept only
> polygons. In that case casting all geometries into multipolygons really
> helps: the layer gets created to accept multipolygons, simple polygons are
> converted into multipolygons with one member, and multipolygons are saved
> as they are. I am not sure if this is the problem that you have, just want
> to clarify that the suggested fix makes sense. See also
> https://github.com/OSGeo/gdal/issues/2828
>
>
>
>
>
> By reading https://mapserver.org/output/ogr_output.html the geometry type
> could be set at LAYER level with
> "ows_geomtype" "MultiPolygon"
>
>
>
> -Jukka Rahkonen-
>
>
>
> *Lähettäjä:* MapServer-users <mapserver-users-bounces at lists.osgeo.org> *Puolesta
> *Benedek Petrovicz
> *Lähetetty:* torstai 22. kesäkuuta 2023 11.17
> *Vastaanottaja:* Scott <public at postholer.com>
> *Kopio:* mapserver-users at lists.osgeo.org
> *Aihe:* Re: [MapServer-users] FlatGeobuf as output format
>
>
>
> I'm not trying to create any fgb-s, but MapServer is.
>
> And the issue is with MultiPolygons, so converting everything to that type
> doesn't help.
>
>
>
> The data source is not fgb. It can be anything.
>
> It is an MSSQL DB in my instance.
>
>
>
> Btw, converting the same dataset to fgb manually with ogr2ogr does work,
> and it doesn't require any extra parameters.
>
> Isn't MapServer using ogr2ogr functionality for OGR based OUTPUTFORMATs?
>
>
>
> I feel like it could handle it, but just hangs up because it sees
> MultiPolygon when checking the type.
>
>
>
> On Wed, Jun 21, 2023 at 6:43 PM Scott <public at postholer.com> wrote:
>
> I'm not sure how you're creating your fgb's, but from an ogr2ogr context
> try promoting all geoms to multi:
>
> -nlt PROMOTE_TO_MULTI
>
> On 6/21/23 07:50, Benedek Petrovicz wrote:
> > Hi!
> >
> > I'm trying to integrate OGR's FlatGeobuf driver as an output format in
> > my mapfiles.
> > It works for the most part and it's awesome, but it fails immediately
> > when I feed some MultiPolygons into it.
> >
> > The geometries are queried from an MSSQL DB.
> >
> > I get the following error:
> > msOGRWriteShape(): OGR error. Attempt to write feature failed (code=6):
> > ICreateFeature: Mismatched geometry type msCalculateScale(): General
> > error message. Invalid image width or height.
> >
> > I found a little note in the docs which corresponds with this issue
> > (https://mapserver.org/input/vector/ogr.html
> > <https://mapserver.org/input/vector/ogr.html>):
> > /"Even though MapInfo and other OGR data sources may support layers with
> > mixed geometry types (e.g. points, lines and polygons in the same file)
> > this is not yet supported in MapServer. So you still have to define a
> > layer ‘TYPE’ and make sure that all the shapes in the OGR data source
> > are compatible with that layer type, otherwise MapServer may produce an
> > error about incompatible geometry types at runtime."/
> > /
> > /
> > So it fails for me when I have Polygons and MultiPolygons in the table
> > I'm querying.
> > But it also fails if it includes MultiPolygons only. So with no mixing
> > of types.
> >
> > I'm using the POLYGON type for my layer in the mapfile.
> >
> > The same dataset works fine when I'm using the GML2 output format. Even
> > with mixing Polygons and MultiPolygons.
> >
> > Am I doing something wrong here?
> > Is it a known limitation for MultiPolygons?
> > Is there a way to bypass the issue while retaining the geometries in the
> DB?
> >
> > Thank you
> > Petrovicz
> >
> > _______________________________________________
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> > MapServer-users at lists.osgeo.org
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