recommit from postgresql repo

src/pg/sql/15_tinmap.sql

@@ -0,0 +1,43 @@
+CREATE OR REPLACE FUNCTION CDB_TINmap(
+    IN geomin geometry[],
+    IN colin numeric[],
+    IN iterations integer
+    )
+RETURNS TABLE(geomout geometry, colout numeric)  AS $$
+DECLARE
+    p geometry[];
+    vals numeric[];
+    gs geometry[];
+    g geometry;
+    vertex geometry[];
+    centerval numeric;
+    va numeric;
+    vb numeric;
+    vc numeric;
+    coltemp numeric[];
+BEGIN
+    SELECT array_agg(dens.geomout), array_agg(dens.colout) INTO p, vals FROM CDB_Densify(geomin, colin, iterations) dens;
+    WITH    a as (SELECT unnest(p) AS e),
+            b as (SELECT ST_DelaunayTriangles(ST_Collect(a.e),0.001, 0) AS t FROM a),
+            c as (SELECT (ST_Dump(t)).geom AS v FROM b)
+        SELECT array_agg(v) INTO gs FROM c;
+    FOREACH g IN ARRAY gs
+    LOOP
+        -- retrieve the vertex of each triangle
+        WITH a AS (SELECT (ST_DumpPoints(g)).geom AS v)
+            SELECT array_agg(v) INTO vertex FROM a;
+        -- retrieve the value of each vertex
+        WITH a AS(SELECT unnest(p) as geo, unnest(vals) as c)
+            SELECT c INTO va FROM a WHERE ST_Equals(geo, vertex[1]);
+        WITH a AS(SELECT unnest(p) as geo, unnest(vals) as c)
+            SELECT c INTO vb FROM a WHERE ST_Equals(geo, vertex[2]);
+        WITH a AS(SELECT unnest(p) as geo, unnest(vals) as c)
+            SELECT c INTO vc FROM a WHERE ST_Equals(geo, vertex[3]);
+        -- calc the value at the center
+        centerval := (va + vb + vc) / 3;
+        -- append the value
+        coltemp := array_append(coltemp, centerval);
+    END LOOP;
+    RETURN QUERY SELECT unnest(gs) as geomout, unnest(coltemp ) as colout;
+END;
+$$ language plpgsql IMMUTABLE;