H2GIS

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ST_LineMerge

Signatures

MULTILINESTRING ST_LineMerge(GEOMETRY geom);

Description

Merges a collection of LINESTRING elements in order to create a new collection of maximal-length LINESTRINGs.

If the user provide something else than (MULTI)LINESTRING it returns an EMPTY MULTILINESTRING.

Examples

Case with a LINESTRING
SELECT ST_LineMerge('LINESTRING (1 1, 1 4)') as THE_GEOM;
-- Answer: MULTILINESTRING ((1 1, 1 4))
Case with a MULTILINESTRING
SELECT ST_LineMerge('MULTILINESTRING ((1 1, 1 4), 
  				      (1 4, 5 4), 
  				      (5 4, 5 1), 
  				      (3 3, 3 4))') as THE_GEOM;
-- Answer: MULTILINESTRING ((1 1, 1 4, 5 4, 5 1), 
--                          (3 3, 3 4))

Case with mixed dimension geometries
SELECT ST_LineMerge('GEOMETRYCOLLECTION (
			LINESTRING (1 1, 1 4), 
			POLYGON ((2 4, 4 4, 4 2, 2 2, 2 4)))');
-- Answer: MULTILINESTRING EMPTY
See also