speed up reverse lookup of place nodes

Add a special index that contains the place nodes buffered by their
respective area according to their search rank. This replaces the
maximum area search for place nodes and reduces drastically the number
of place nodes that need to be retrieved.

lib-sql/indices.sql

@@ -30,6 +30,13 @@ CREATE INDEX IF NOT EXISTS idx_placex_geometry_reverse_lookupPolygon
     AND rank_address between 4 and 25 AND type != 'postcode'
     AND name is not null AND indexed_status = 0 AND linked_place_id is null;
 ---
+-- used in reverse large area lookup
+CREATE INDEX IF NOT EXISTS idx_placex_geometry_reverse_lookupPlaceNode
+  ON placex USING gist (ST_Buffer(geometry, reverse_place_diameter(rank_search)))
+  {{db.tablespace.search_index}}
+  WHERE rank_address between 4 and 25 AND type != 'postcode'
+    AND name is not null AND linked_place_id is null AND osm_type = 'N';
+---
 CREATE INDEX IF NOT EXISTS idx_osmline_parent_place_id
   ON location_property_osmline USING BTREE (parent_place_id) {{db.tablespace.search_index}}
   WHERE parent_place_id is not null;

lib-sql/tables.sql

@@ -190,7 +190,6 @@ CREATE INDEX idx_placex_geometry_buildings ON placex
 
 -- Usage: - linking of similar named places to boundaries
 --        - linking of place nodes with same type to boundaries
---        - lookupPolygon()
 CREATE INDEX idx_placex_geometry_placenode ON placex
   USING {{postgres.spgist_geom}} (geometry) {{db.tablespace.address_index}}
   WHERE osm_type = 'N' and rank_search < 26