Name

ST_SharedPaths — Returns a collection containing paths shared by the two input linestrings/multilinestrings.

Synopsis

geometry ST_SharedPaths(geometry lineal1, geometry lineal2);

Description

Returns a collection containing paths shared by the two input geometries. Those going in the same direction are in the first element of the collection, those going in the opposite direction are in the second element. The paths themselves are given in the direction of the first geometry.

Performed by the GEOS module.

Availability: 2.0.0

Examples: Finding shared paths

Adjacent shared path segments may be returned as separate or merged LineStrings depending on the GEOS version.

Find the shared paths of a MultiLineString and a LineString.

Code
SELECT ST_SharedPaths(ST_GeomFromText('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),
      (51 150,101 150,76 175,51 150))'),
   ST_GeomFromText('LINESTRING(151 100,126 156.25,126 125,101 150,76 175)')
   )
Output
GEOMETRYCOLLECTION(MULTILINESTRING((126 156.25,126 125),
(101 150,76 175)),MULTILINESTRING EMPTY)
Figure
Geometry figure for visual-st-sharedpaths-01

Flip the LineString orientation to return the same paths in the opposite-direction member.

Code
SELECT ST_SharedPaths(ST_GeomFromText('LINESTRING(76 175,101 150,126 125,126 156.25,151 100)'),
   ST_GeomFromText('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),
       (51 150,101 150,76 175,51 150))')
    )
Output
GEOMETRYCOLLECTION(MULTILINESTRING EMPTY,
MULTILINESTRING((76 175,101 150),(126 125,126 156.25)))
Figure
Geometry figure for visual-st-sharedpaths-02