ST_Subdivide
Name
ST_Subdivide — Returns a set of geometry where no geometry in the set has more than the specified number of vertices.
Synopsis
setof geometry
ST_Subdivide
(
geometry
geom
, integer
max_vertices=256
)
;
Description
Divides geometry into parts until a part can be represented using no more than
max_vertices
.
Point-in-polygon and other overlay operations are normally faster for indexed subdivided dataset:
"miss" cases are faster to check as boxes for all parts typically cover smaller area than original geometry box,
"hit" cases are faster because recheck operates on less points.
Uses the same envelope clipping as
ST_ClipByBox2D
.
max_vertices
must be 5 or more, as 5 points are needed to represent a closed box.
Performed by the GEOS module.
Availability: 2.2.0
Enhanced: 2.5.0 reuses existing points on polygon split, vertex count is lowered from 8 to 5.
Examples
-- Subdivide complex geometries in table, in place
with complex_areas_to_subdivide as (
delete from polygons_table
where ST_NPoints(geom) > 255
returning id, column1, column2, column3, geom
)
insert into polygons_table (fid, column1, column2, column3, geom)
select
fid, column1, column2, column3,
ST_Subdivide(geom, 255) as geom
from complex_areas_to_subdivide;
-- Create a new subdivided table suitable for joining to the original CREATE TABLE subdivided_geoms AS SELECT pkey, ST_Subdivide(geom) AS geom FROM original_geoms;
Subdivide max 10 vertices
SELECT row_number() OVER() As rn, ST_AsText(geom) As wkt
FROM ( SELECT ST_SubDivide('POLYGON((132 10,119 23,85 35,68 29,66 28,49 42,32 56,22 64,32 110,40 119,36 150,
57 158,75 171,92 182,114 184,132 186,146 178,176 184,179 162,184 141,190 122,
190 100,185 79,186 56,186 52,178 34,168 18,147 13,132 10))'::geometry,10)) As f(geom);
rn │ wkt ────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────── 1 │ POLYGON((119 23,85 35,68 29,66 28,32 56,22 64,29.8260869565217 100,119 100,119 23)) 2 │ POLYGON((132 10,119 23,119 56,186 56,186 52,178 34,168 18,147 13,132 10)) 3 │ POLYGON((119 56,119 100,190 100,185 79,186 56,119 56)) 4 │ POLYGON((29.8260869565217 100,32 110,40 119,36 150,57 158,75 171,92 182,114 184,114 100,29.8260869565217 100)) 5 │ POLYGON((114 184,132 186,146 178,176 184,179 162,184 141,190 122,190 100,114 100,114 184))
|
Useful in conjunction with ST_Segmentize(geography) to create additional vertices that can then be used for splitting.
SELECT ST_AsText(ST_Subdivide(ST_Segmentize('LINESTRING(0 0, 85 85)'::geography,1200000)::geometry,8));
LINESTRING(0 0,0.487578359029357 5.57659056746196,0.984542144675897 11.1527721155093,1.50101059639722 16.7281035483571,1.94532113630331 21.25) LINESTRING(1.94532113630331 21.25,2.04869538062779 22.3020741387339,2.64204641967673 27.8740533545155,3.29994062412787 33.443216802941,4.04836719489742 39.0084282520239,4.59890468420694 42.5) LINESTRING(4.59890468420694 42.5,4.92498503922732 44.5680389206321,5.98737409390639 50.1195229244701,7.3290919767674 55.6587646879025,8.79638749938413 60.1969505994924) LINESTRING(8.79638749938413 60.1969505994924,9.11375579533779 61.1785363177625,11.6558166691368 66.6648504160202,15.642041247655 72.0867690601745,22.8716627200212 77.3609628116894,24.6991785131552 77.8939011989848) LINESTRING(24.6991785131552 77.8939011989848,39.4046096622744 82.1822848017636,44.7994523421035 82.5156766227011) LINESTRING(44.7994523421035 82.5156766227011,85 85)
|