I try to add a constraint based on geometry type to a "street" table that prevents anything except Linestring geometry or Null.

alter table streets
add constraint streets_geom_linestring_chk
check(st_geometrytype(geom) = 'ST_LINESTRING'::text OR geom IS NULL);

When I try to store geometries in the table:

update streets set geom=st_geomfromtext('LINESTRING(0 8,12 8)') where id=1;

I got an error, that the new row for relation violates check constraint.

  • 1
    Please edit your question and add a more descriptive title. Titles should be written as questions.
    – underdark
    Commented Feb 24, 2014 at 15:41

1 Answer 1


ST_GeometryType returns 'ST_Linestring', 'ST_Polygon','ST_MultiPolygon' etc. You can change check to use GeometryType which return mentioned values without ST_ prefix

  • Yes of course, the solution is the st_ prefix in the geometrytype function. I had already tried to remove the st_ in linestring and add a st_ at the input. sometimes the solution is so simple. many thanks for the quick response.
    – surfer_cid
    Commented Feb 24, 2014 at 12:55

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