PostGIS

AddFace
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AddFace

10.8. Topology Processing

Name

AddFace — Registers a face primitive to a topology and gets its identifier.

Synopsis

integer +`*`+AddFace*(`varchar `toponame, geometry apolygon, boolean force_new=false`)`;

Description

Registers a face primitive to a topology and gets its identifier.

For a newly added face, the edges forming its boundaries and the ones contained in the face will be updated to have correct values in the left_face and right_face fields. Isolated nodes contained in the face will also be updated to have a correct containing_face field value.

This function does not use nor set the next_left_edge and next_right_edge fields of the edge table.

The target topology is assumed to be valid (containing no self-intersecting edges). An exception is raised if: The polygon boundary is not fully defined by existing edges or the polygon overlaps an existing face.

If the apolygon geometry already exists as a face, then: if force_new is false (the default) the face id of the existing face is returned; if force_new is true a new id will be assigned to the newly registered face.

When a new registration of an existing face is performed (force_new=true), no action will be taken to resolve dangling references to the existing face in the edge, node an relation tables, nor will the MBR field of the existing face record be updated. It is up to the caller to deal with that.

The apolygon geometry must have the same srid as defined for the topology otherwise an invalid spatial reference sys error will be thrown.

Availability: 2.0.0

Examples

-- first add the edges we use generate_series as an iterator (the below
-- will only work for polygons with < 10000 points because of our max in gs)
SELECT topology.AddEdge('ma_topo', ST_MakeLine(ST_PointN(geom,i), ST_PointN(geom, i + 1) )) As edgeid
    FROM (SELECT  ST_NPoints(geom) AS npt, geom
            FROM
                (SELECT ST_Boundary(ST_GeomFromText('POLYGON((234896.5 899456.7,234914 899436.4,234946.6 899356.9,234872.5 899328.7,
                234891 899285.4,234992.5 899145, 234890.6 899069,234755.2 899255.4,
                234612.7 899379.4,234776.9 899563.7,234896.5 899456.7))', 26986) )  As geom
            )  As geoms) As facen CROSS JOIN generate_series(1,10000) As i
         WHERE i < npt;
-- result --
 edgeid
--------
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
(10 rows)
-- then add the face -

SELECT topology.AddFace('ma_topo',
    ST_GeomFromText('POLYGON((234896.5 899456.7,234914 899436.4,234946.6 899356.9,234872.5 899328.7,
    234891 899285.4,234992.5 899145, 234890.6 899069,234755.2 899255.4,
    234612.7 899379.4,234776.9 899563.7,234896.5 899456.7))', 26986) ) As faceid;
-- result --
faceid
--------
 1

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