ST_LongestAxisPolygonsFromVoronoiDiagrams_gs

DROP FUNCTION IF EXISTS ST_LongestAxisPolygonsFromVoronoiDiagrams_gs(
    geom GEOMETRY,
    n integer)

CREATE OR REPLACE FUNCTION ST_LongestAxisPolygonsFromVoronoiDiagrams_gs(
    geom GEOMETRY,
    n integer)
RETURNS GEOMETRY AS
$BODY$
    WITH
        tbla AS (SELECT (ST_Dump($1)).geom),
        tblb AS (WITH btbl AS (SELECT (ST_ExteriorRing(((ST_Dump(geom)).geom))) geom),
            intervals AS (SELECT generate_series (0, n) as steps)
            SELECT steps AS stp, ST_LineInterpolatePoint(geom, steps/(SELECT count(steps)::float-1 FROM intervals)) geom FROM btbl, intervals GROUP BY intervals.steps, geom),
        tblc AS (SELECT ((ST_Dump(ST_VoronoiPolygons(ST_Collect(geom)))).geom) geom FROM tblb),
        tbld AS (SELECT (ST_Dump(ST_Intersection(a.geom, b.geom))).geom FROM tblc a JOIN tbla b ON ST_Intersects(a.geom, b.geom)),
        tble AS (SELECT line1, line2 FROM (SELECT ST_MakeLine((ST_PointN(ST_Boundary(ST_OrientedEnvelope(geom)),1)),
        (ST_PointN(ST_Boundary(ST_OrientedEnvelope(geom)),2))) AS line1, ST_MakeLine((ST_PointN(ST_Boundary(ST_OrientedEnvelope(geom)),2)), (ST_PointN(ST_Boundary(ST_OrientedEnvelope(geom)),3))) AS line2 FROM tbla) AS foo),
        tblf AS (SELECT (ST_Buffer(line2, ST_Length(line2), 'endcap=flat join=round')) geom FROM tble),
        tblg AS (SELECT DISTINCT (ST_Dump(ST_Difference(a.geom, b.geom))).geom FROM tblf a JOIN tbla b ON ST_Intersects(a.geom, b.geom)),
        tblh AS (SELECT (ST_Dump(ST_Buffer(geom, -0.000001))).geom geom FROM tblg),
        tbli AS (SELECT (ST_Buffer(geom, 0.000002)) geom FROM tblh a JOIN tble b ON ST_Intersects(a.geom, b.line2)),
        tblj AS (SELECT ST_ExteriorRing(ST_Union(a.geom)) geom FROM tbld a JOIN tbli b ON ST_Intersects(a.geom, b.geom)),
        tblk AS (SELECT ST_MakeLine(pt1, pt2) geom FROM (SELECT ST_PointN(geom, generate_series(1, ST_NPoints(geom)-1)) pt1, ST_PointN(geom, generate_series(2, ST_NPoints(geom))) pt2 FROM tblj) AS geom),
        tbll AS (SELECT (ST_Dump(ST_Intersection(ST_Buffer(a.geom, -0.0001), b.geom))).geom FROM tbla a JOIN tblk b ON ST_Contains(a.geom, b.geom))
        SELECT ST_MakeLine(ST_Centroid(geom)) geom FROM tbll;
$BODY$
LANGUAGE SQL

SELECT ST_LongestAxisPolygonsFromVoronoiDiagrams_gs(geom, 300) geom FROM <source_table>