2020-07-02 15:03:16 +10:00

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{
"name": "boundary",
"type": "function",
"groups": ["GeometryGroup"],
"description":"Returns the closure of the combinatorial boundary of the geometry (ie the topological boundary of the geometry). For instance, a polygon geometry will have a boundary consisting of the linestrings for each ring in the polygon. Some geometry types do not have a defined boundary, e.g., points or geometry collections, and will return null.",
"arguments": [ {"arg":"geometry","description":"a geometry"} ],
"examples": [ { "expression":"geom_to_wkt(boundary(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))')))", "returns":"'LineString(1 1,0 0,-1 1,1 1)'"}]
}