PostGIS

ST_PatchN
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ST_PatchN

8.4. Geometry Accessors

Name

ST_PatchN — Returns the Nth geometry (face) of a PolyhedralSurface.

Synopsis

geometry +`*`+ST_PatchN*(`geometry `geomA, integer n`)`;

Description

Returns the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE or POLYHEDRALSURFACEM. Otherwise, returns NULL. This returns the same answer as ST_GeometryN for PolyhedralSurfaces. Using ST_GeometryN is faster.

Note

Index is 1-based.

If you want to extract all elements of a geometry ST_Dump is more efficient.

Availability: 2.0.0

check This method implements the SQL/MM specification. SQL-MM ISO/IEC 13249-3: 8.5

check This function supports 3d and will not drop the z-index.

check This function supports Polyhedral surfaces.

Examples

--Extract the 2nd face of the polyhedral surface
SELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewkt
FROM (
VALUES (ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ) As foo(geom);

              geomewkt
---+-----------------------------------------
 POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

PostGIS

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