cdb_union_adgacent

pg/sql/0.0.1/05_cdb_union_adjacent.sql

@@ -0,0 +1,43 @@
+CREATE OR REPLACE FUNCTION _cdb_final_union_adjacent( joined_geoms geometry[] )
+RETURNS geometry[] AS $$
+BEGIN
+    RETURN joined_geoms;
+END
+$$ LANGUAGE plpgsql;
+
+
+CREATE OR REPLACE FUNCTION _cdb_state_update_union_adjacent(clusters geometry[], new_geom  geometry)
+RETURNS geometry[] AS $$
+DECLARE
+  joins  geometry[] :='{}';
+  unjoined geometry[] :='{}';
+  i integer;
+  combined geometry;
+BEGIN
+  joins := (select array_agg(g)
+            from unnest(clusters) a(g)
+            where ST_TOUCHES(g, new_geom));
+
+  unjoined := (select array_agg(g)
+               from unnest(clusters) a(g)
+               where ST_TOUCHES(g, new_geom) = false);
+
+  IF array_length(joins, 1) > 0 THEN
+    joins := array_append(joins, new_geom);
+    combined := ST_UNION(joins);
+  ELSE
+    combined := new_geom;
+  END IF;
+
+  unjoined := array_append(unjoined, combined);
+  RETURN unjoined;
+END
+$$
+LANGUAGE plpgsql;
+
+CREATE AGGREGATE cdb_union_adjacent(geometry)(
+  SFUNC=_cdb_state_update_union_adjacent,
+  STYPE=geometry[],
+  FINALFUNC=_cdb_final_union_adjacent,
+  INITCOND='{}'
+);