sql - Constructing Voronoi diagram in PostGIS

I'm trying to construct voronoi diagram from grid of points using modified code from here. This is SQL query after my modifications:

DROP TABLE IF EXISTS example.voronoi;
WITH 
    -- Sample set of points to work with
    Sample AS (SELECT ST_SetSRID(ST_Union(geom), 0) geom FROM example."MeshPoints2d"),
    -- Build edges and circumscribe points to generate a centroid
    Edges AS (
    SELECT id,
        UNNEST(ARRAY['e1','e2','e3']) EdgeName,
        UNNEST(ARRAY[

            ST_MakeLine(p1,p2) ,
            ST_MakeLine(p2,p3) ,
            ST_MakeLine(p3,p1)]) Edge,
        ST_Centroid(ST_ConvexHull(ST_Union(-- Done this way due to issues I had with LineToCurve
            ST_CurveToLine(REPLACE(ST_AsText(ST_LineMerge(ST_Union(ST_MakeLine(p1,p2),ST_MakeLine(p2,p3)))),'LINE','CIRCULAR'),15),
            ST_CurveToLine(REPLACE(ST_AsText(ST_LineMerge(ST_Union(ST_MakeLine(p2,p3),ST_MakeLine(p3,p1)))),'LINE','CIRCULAR'),15)
        ))) ct      
    FROM    (
        -- Decompose to points
        SELECT id,

            ST_PointN(g,1) p1,
            ST_PointN(g,2) p2,
            ST_PointN(g,3) p3
        FROM    (
            SELECT (gd).Path id, ST_ExteriorRing((gd).geom) g -- ID andmake triangle a linestring
            FROM (SELECT (ST_Dump(ST_DelaunayTriangles(geom))) gd FROM Sample) a -- Get Delaunay Triangles
            )b
        ) c
    )
SELECT ST_SetSRID((ST_Dump(ST_Polygonize(ST_Node(ST_LineMerge(ST_Union(v, ST_ExteriorRing(ST_ConvexHull(v)))))))).geom, 2180)

INTO example.voronoi
FROM (
    SELECT  -- Create voronoi edges and reduce to a multilinestring
        ST_LineMerge(ST_Union(ST_MakeLine(
        x.ct,
        CASE 
        WHEN y.id IS NULL THEN
            CASE WHEN ST_Within(
                x.ct,
                (SELECT ST_ConvexHull(geom) FROM sample)) THEN -- Don't draw lines back towards the original set

                -- Project line out twice the distance from convex hull
                ST_MakePoint(ST_X(x.ct) + ((ST_X(ST_Centroid(x.edge)) - ST_X(x.ct)) * 2),ST_Y(x.ct) + ((ST_Y(ST_Centroid(x.edge)) - ST_Y(x.ct)) * 2))
            END
        ELSE 
            y.ct
        END
        ))) v
    FROM    Edges x 
        LEFT OUTER JOIN -- Self Join based on edges
        Edges y ON x.id <> y.id AND ST_Equals(x.edge,y.edge)

    ) z

Below - result of my query.

As you can see I get "almost" correct voronoi diagram, except highlighted points which don't have unique polygon. Below is what QGIS algorithm produce and what I would like to obtain from query. Any sugestions where is the problem with my code?

Answer

While this fixes the immediate issue with the query for the data in question, I am not happy with it as a solution for general usage and I will revisit this and the previous answer when I can.

The issue was that the original query was using a convex hull on the voronoi edges to determine the exterior edge for the voronoi polygon. This meant that some of the voronoi edges weren't reaching the exterior when they should have been. I looked at using the concave hull functionality, but it didn't really work as I wanted.
As a quick fix I have changed convex hull to be built around the closed set of voronoi edges plus a buffer around the original edges. The voronoi edges that don't close are extended out a large distance to try and make sure that they intersect the exterior and are use to build polygons. You may want to play around with the buffer parameters.

WITH 

    -- Sample set of points to work with
    Sample AS (SELECT ST_SetSRID(ST_Union(geom), 0) geom FROM MeshPoints2d),
    -- Build edges and circumscribe points to generate a centroid
    Edges AS (
    SELECT id,
        UNNEST(ARRAY['e1','e2','e3']) EdgeName,
        UNNEST(ARRAY[
            ST_MakeLine(p1,p2) ,
            ST_MakeLine(p2,p3) ,
            ST_MakeLine(p3,p1)]) Edge,

        ST_Centroid(ST_ConvexHull(ST_Union(-- Done this way due to issues I had with LineToCurve
            ST_CurveToLine(REPLACE(ST_AsText(ST_LineMerge(ST_Union(ST_MakeLine(p1,p2),ST_MakeLine(p2,p3)))),'LINE','CIRCULAR'),15),
            ST_CurveToLine(REPLACE(ST_AsText(ST_LineMerge(ST_Union(ST_MakeLine(p2,p3),ST_MakeLine(p3,p1)))),'LINE','CIRCULAR'),15)
        ))) ct      
    FROM    (
        -- Decompose to points
        SELECT id,
            ST_PointN(g,1) p1,
            ST_PointN(g,2) p2,
            ST_PointN(g,3) p3

        FROM    (
            SELECT (gd).Path id, ST_ExteriorRing((gd).geom) g -- ID andmake triangle a linestring
            FROM (SELECT (ST_Dump(ST_DelaunayTriangles(geom))) gd FROM Sample) a -- Get Delaunay Triangles
            )b
        ) c
    )
SELECT ST_SetSRID((ST_Dump(ST_Polygonize(ST_Node(ST_LineMerge(ST_Union(v, (SELECT ST_ExteriorRing(ST_ConvexHull(ST_Union(ST_Union(ST_Buffer(edge,20),ct)))) FROM Edges))))))).geom, 2180) geom
INTO voronoi
FROM (
    SELECT  -- Create voronoi edges and reduce to a multilinestring

        ST_LineMerge(ST_Union(ST_MakeLine(
        x.ct,
        CASE 
        WHEN y.id IS NULL THEN
            CASE WHEN ST_Within(
                x.ct,
                (SELECT ST_ConvexHull(geom) FROM sample)) THEN -- Don't draw lines back towards the original set
                -- Project line out twice the distance from convex hull
                ST_MakePoint(ST_X(x.ct) + ((ST_X(ST_Centroid(x.edge)) - ST_X(x.ct)) * 200),ST_Y(x.ct) + ((ST_Y(ST_Centroid(x.edge)) - ST_Y(x.ct)) * 200))
            END

        ELSE 
            y.ct
        END
        ))) v
    FROM    Edges x 
        LEFT OUTER JOIN -- Self Join based on edges
        Edges y ON x.id <> y.id AND ST_Equals(x.edge,y.edge)
    ) z;