In a PostGIS table with a geometry column of type 'Geometry' containing MultiLineStrings and MultiPolygons QGIS wants to load these as MultiCurve and MultiSurface layers. When I create a new object on one of these layers it is of type MultiCurve or MultiSurface. However I would like MultiLineStrings and MultiPolygons for compatibility with other processes e.g. filtering objects by geometry type.

I can not change the Spatial Type in the Data Source Manager. I'm running 3.28.1. What can I do to force creation of MultiLineStrings and MultiPolygons instead of MultiCurves and MultiSurfaces?

1 Answer 1


I had the same problem : I used a trigger to convert multisurfaces into multipolygons when I create features. For the function :

CREATE FUNCTION myConvert() returns trigger as
 IF st_geometrytype(NEW.geom) like '%surface%' THEN NEW.geom = st_multi(st_curvetoLine(NEW.geom))

Then create the trigger.

  • Nice function. I was using st_curvetoline() manually. I was hoping to do it in QGIS but this at least makes it a lot easier to do in PostGIS. Thanks. Nov 21, 2022 at 16:35

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