ST_ToMultiSegments
Signatures
MULTILINESTRING ST_ToMultiSegments(GEOMETRY geom);
MULTILINESTRING ST_ToMultiSegments(GEOMETRYCOLLECTION geom);
Description
Converts geom
into a set of distinct segments stored in a MULTILINESTRING
.
Returns MULTILINESTRING EMPTY
for Geometries of dimension 0.
Examples
SELECT ST_ToMultiSegments('LINESTRING(5 4, 1 1, 3 4, 4 5)');
-- Answer: MULTILINESTRING((5 4, 1 1), (1 1, 3 4), (3 4, 4 5))
SELECT ST_ToMultiSegments(
'MULTILINESTRING((1 4 3, 15 7 9, 16 17 22),
(0 0 0, 1 0 0, 1 2 0, 0 2 1))');
-- Answer: MULTILINESTRING((1 4, 15 7), (15 7, 16 17),
-- (0 0, 1 0), (1 0, 1 2), (1 2, 0 2))
SELECT ST_ToMultiSegments(
'POLYGON((0 0, 10 0, 10 6, 0 6, 0 0),
(1 1, 2 1, 2 5, 1 5, 1 1))');
-- Answer: MULTILINESTRING((0 0, 10 0), (10 0, 10 6), (10 6, 0 6),
-- (0 6, 0 0), (1 1, 2 1), (2 1, 2 5),
-- (2 5, 1 5), (1 5, 1 1))
SELECT ST_ToMultiSegments(
'GEOMETRYCOLLECTION(
POLYGON((0 0, 10 0, 10 5, 0 5, 0 0),
(1 1, 2 1, 2 4, 1 4, 1 1),
(7 1, 8 1, 8 3, 7 3, 7 1)),
POINT(2 3),
LINESTRING(8 7, 9 5, 11 3))');
-- Answer:MULTILINESTRING((0 0, 10 0), (10 0, 10 5), (10 5, 0 5),
-- (0 5, 0 0), (1 1, 2 1), (2 1, 2 4),
-- (2 4, 1 4), (1 4, 1 1), (7 1, 8 1),
-- (8 1, 8 3), (8 3, 7 3), (7 3, 7 1),
-- (8 7, 9 5), (9 5, 11 3))
SELECT ST_ToMultiSegments('POINT(5 5)');
-- Answer: MULTILINESTRING EMPTY
Comparison with ST_ToMultiLine
CREATE TABLE input(poly POLYGON);
INSERT INTO input VALUES (
'POLYGON((0 0, 10 0, 10 6, 0 6, 0 0),
(1 1, 2 1, 2 5, 1 5, 1 1),
(7 1, 8 1, 8 3, 7 3, 7 1))');
SELECT ST_ToMultiSegments(poly) SEG,
ST_ToMultiLine(poly) LINE FROM input;
-- Answer:
-- | SEG | LINE |
-- |------------------------------|---------------------------------|
-- |MULTILINESTRING((0 0, 10 0), |MULTILINESTRING |
-- | (10 0, 10 6), (10 6, 0 6),| ((0 0, 10 0, 10 6, 0 6, 0 0),|
-- | (0 6, 0 0), (1 1, 2 1), | (1 1, 2 1, 2 5, 1 5, 1 1), |
-- | (2 1, 2 5), (2 5, 1 5), | (7 1, 8 1, 8 3, 7 3, 7 1)) |
-- | (1 5, 1 1), (7 1, 8 1), | |
-- | (8 1, 8 3), (8 3, 7 3), | |
-- | (7 3, 7 1)) | |