Name
ST_SetPoint — Replace point N of linestring with given point. Index is 0-based.
Synopsis
geometry ST_SetPoint(geometry linestring, integer zerobasedposition, geometry point);
Description
Replace point N of linestring with given point. Index is 0-based. This is especially useful in triggers when trying to maintain relationship of joints when one vertex moves.
Availability: 1.1.0
This function supports 3d and will not drop the z-index.
Examples
--Change first point in line string from -1 3 to -1 1
SELECT ST_AsText(ST_SetPoint('LINESTRING(-1 2,-1 3)', 0, 'POINT(-1 1)'));
st_astext
-----------------------
LINESTRING(-1 1,-1 3)
---Change last point in a line string (lets play with 3d linestring this time)
SELECT ST_AsEWKT(ST_SetPoint(foo.the_geom, ST_NumPoints(foo.the_geom) - 1, ST_GeomFromEWKT('POINT(-1 1 3)')))
FROM (SELECT ST_GeomFromEWKT('LINESTRING(-1 2 3,-1 3 4, 5 6 7)') As the_geom) As foo;
st_asewkt
-----------------------
LINESTRING(-1 2 3,-1 3 4,-1 1 3)