fix: merge holes with neighboring polygons

fmtm_splitter/fmtm_algorithm.sql

@@ -369,7 +369,8 @@ CREATE TABLE taskpolygons AS (
     ),
 
     taskpolygonsnoindex AS (
-        SELECT (ST_DUMP(ST_POLYGONIZE(s.geom))).geom AS geom
+        SELECT
+            (ST_DUMP(ST_POLYGONIZE(s.geom))).geom AS geom
         FROM simplifiedlines AS s
     )
 
@@ -380,13 +381,68 @@ CREATE TABLE taskpolygons AS (
 );
 
 -- ALTER TABLE taskpolygons ADD PRIMARY KEY(taskid);
+
+-- Step 1: Identify polygons without any buildings
+DROP TABLE IF EXISTS no_building_polygons;
+CREATE TABLE no_building_polygons AS (
+    SELECT tp.geom AS no_building_geom, tp.*
+    FROM taskpolygons tp
+    LEFT JOIN buildings b ON ST_Intersects(tp.geom, b.geom)
+    WHERE b.geom IS NULL
+);
+
+-- Step 2: Identify neighboring polygons
+DROP TABLE IF EXISTS neighboring_polygons;
+CREATE TABLE neighboring_polygons AS (
+    SELECT nb.geom AS neighbor_geom, nb.*, nb_building_count, nbp.no_building_geom
+    FROM taskpolygons nb
+    JOIN no_building_polygons nbp
+    ON ST_Touches(nbp.no_building_geom, nb.geom) -- Finds polygons that touch each other
+    LEFT JOIN (
+        -- Step 3: Count buildings in the neighboring polygons
+        SELECT nb.geom, COUNT(b.geom) AS nb_building_count
+        FROM taskpolygons nb
+        LEFT JOIN buildings b ON ST_Intersects(nb.geom, b.geom)
+        GROUP BY nb.geom
+    ) AS building_counts
+    ON nb.geom = building_counts.geom
+);
+
+-- Step 4: Find the optimal neighboring polygon to avoid,
+-- same polygons with the smallest number of buildings merging into multiple neighboring polygons
+DROP TABLE IF EXISTS optimal_neighbors;
+CREATE TABLE optimal_neighbors AS (
+    SELECT nbp.no_building_geom, nbp.neighbor_geom
+    FROM neighboring_polygons nbp
+    WHERE nbp.nb_building_count = (
+        SELECT MIN(nb_building_count)
+        FROM neighboring_polygons np
+        WHERE np.no_building_geom = nbp.no_building_geom
+    )
+);
+
+-- Step 5: Merge the small polygons with their optimal neighboring polygons
+UPDATE taskpolygons tp
+SET geom = ST_Union(tp.geom, nbp.no_building_geom)
+FROM optimal_neighbors nbp
+WHERE tp.geom = nbp.neighbor_geom;
+DELETE FROM taskpolygons
+WHERE geom IN (
+    SELECT no_building_geom
+    FROM no_building_polygons
+);
+
+
+DROP TABLE IF EXISTS no_building_polygons;
+DROP TABLE IF EXISTS neighboring_polygons;
+
 SELECT POPULATE_GEOMETRY_COLUMNS('public.taskpolygons'::regclass);
 CREATE INDEX taskpolygons_idx
 ON taskpolygons
 USING gist (geom);
 -- VACUUM ANALYZE taskpolygons;
 
-
+-- Generate GeoJSON output
 SELECT
     JSONB_BUILD_OBJECT(
         'type', 'FeatureCollection',
@@ -401,3 +457,4 @@ FROM (
         ) AS feature
     FROM taskpolygons
 ) AS features;
+