ST_PatchN
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.
Index is 1-based. |
If you want to extract all elements of a geometry ST_Dump is more efficient. |
Availability: 2.0.0
This method implements the SQL/MM specification.
SQL-MM ISO/IEC 13249-3: 8.5
This function supports 3d and will not drop the z-index.
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))