My question follows from Splitting Streets to Create Polygons?
I was able to successfully convert a layer of linestrings to polygons based on line intersections with the query given in the answer.
SELECT (ST_Dump(ST_Polygonize(ST_Node(multi_geom)))).geom
FROM (
SELECT ST_Collect(<geom>) AS multi_geom
FROM <your_table>
-- WHERE <condition>
-- GROUP BY <attribute>
) q
;
However, I had a problem with ST_Collect and used ST_Union to create a single geometry of lines from the original linestrings. What I noticed was, St_Union is doing the same thing that St_Node does, St_Union creates a single geometry from lines splitting them at intersections. I simply call St_Dumps on the output from St_Union. This is the transformed query:
SELECT (ST_Dump(ST_Polygonize(q.geom))).geom geom FROM (SELECT ST_Union(geom) geom FROM streets
Are St_Union and St_Node (with regards to this specific operation) similar or is there any benefit from using one over the other?
