Name
ST_Split — Returns a collection of geometries resulting by splitting a geometry.
Synopsis
geometry ST_Split(geometry input, geometry blade);
Description
The function supports splitting a line by point, a line by line, a polygon by line. The returned geometry is always a collection.
Think of this function as the opposite of ST_Union. Theoretically applying ST_Union to the elements of the returned collection should always yield the original geometry.
Availability: 2.0.0
Examples
Polygon Cut by Line
|
 Before Split
|
 After split
|
-- this creates a geometry collection consisting of the 2 halves of the polygon
-- this is similar to the example we demonstrated in ST_BuildArea
SELECT ST_Split(circle, line)
FROM (SELECT
ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)) As line,
ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As circle) As foo;
-- result --
GEOMETRYCOLLECTION(POLYGON((150 90,149.039264020162 80.2454838991936,146.193976625564 70.8658283817455,..), POLYGON(..)))
-- To convert to individual polygons, you can use ST_Dump or ST_GeometryN
SELECT ST_AsText((ST_Dump(ST_Split(circle, line))).geom) As wkt
FROM (SELECT
ST_MakeLine(ST_MakePoint(10, 10),ST_MakePoint(190, 190)) As line,
ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50) As circle) As foo;
-- result --
wkt
---------------
POLYGON((150 90,149.039264020162 80.2454838991936,..))
POLYGON((60.1371179574584 60.1371179574584,58.4265193848728 62.2214883490198,53.8060233744357 ..))
Multilinestring Cut by point
|
 Before Split
|
 After split
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SELECT ST_AsText(ST_Split(mline, pt)) As wktcut
FROM (SELECT
ST_GeomFromText('MULTILINESTRING((10 10, 190 190), (15 15, 30 30, 100 90))') As mline,
ST_Point(30,30) As pt) As foo;
wktcut
------
GEOMETRYCOLLECTION(
LINESTRING(10 10,30 30),
LINESTRING(30 30,190 190),
LINESTRING(15 15,30 30),
LINESTRING(30 30,100 90)
)