reorganise layout of location_postcode table

Also renames the table as this will make it easier to migrate.

lib-sql/functions.sql

@@ -2,7 +2,7 @@
 --
 -- This file is part of Nominatim. (https://nominatim.org)
 --
--- Copyright (C) 2022 by the Nominatim developer community.
+-- Copyright (C) 2025 by the Nominatim developer community.
 -- For a full list of authors see the git log.
 
 {% include('functions/utils.sql') %}
@@ -18,7 +18,7 @@
     {% include 'functions/placex_triggers.sql' %}
 {% endif %}
 
-{% if 'location_postcode' in db.tables %}
+{% if 'location_postcodes' in db.tables %}
     {% include 'functions/postcode_triggers.sql' %}
 {% endif %}
 

lib-sql/functions/placex_triggers.sql

@@ -1399,7 +1399,7 @@ BEGIN
 
   {% if debug %}RAISE WARNING 'placex_delete:12 % %',OLD.osm_type,OLD.osm_id;{% endif %}
 
-  UPDATE location_postcode SET indexed_status = 2 WHERE parent_place_id = OLD.place_id;
+  UPDATE location_postcodes SET indexed_status = 2 WHERE parent_place_id = OLD.place_id;
 
   RETURN OLD;
 

lib-sql/functions/utils.sql

@@ -139,37 +139,46 @@ $$
 LANGUAGE plpgsql IMMUTABLE PARALLEL SAFE;
 
 
--- Find the nearest artificial postcode for the given geometry.
--- TODO For areas there should not be more than two inside the geometry.
+-- Find the best-matching postcode for the given geometry
 CREATE OR REPLACE FUNCTION get_nearest_postcode(country VARCHAR(2), geom GEOMETRY)
   RETURNS TEXT
   AS $$
 DECLARE
   outcode TEXT;
   cnt INTEGER;
+  location RECORD;
 BEGIN
     -- If the geometry is an area then only one postcode must be within
     -- that area, otherwise consider the area as not having a postcode.
     IF ST_GeometryType(geom) in ('ST_Polygon','ST_MultiPolygon') THEN
-        SELECT min(postcode), count(*) FROM
-              (SELECT postcode FROM location_postcode
-                WHERE ST_Contains(geom, location_postcode.geometry) LIMIT 2) sub
-          INTO outcode, cnt;
+      SELECT min(postcode), count(*) FROM
+        (SELECT postcode FROM location_postcodes
+           WHERE geom && location_postcodes.geometry -- want to use the index
+                 AND ST_Contains(geom, location_postcodes.centroid)
+                 AND country_code = country
+           LIMIT 2) sub
+        INTO outcode, cnt;
 
         IF cnt = 1 THEN
             RETURN outcode;
-        ELSE
-            RETURN null;
         END IF;
+
+        RETURN null;
     END IF;
 
-    SELECT postcode FROM location_postcode
-     WHERE ST_DWithin(geom, location_postcode.geometry, 0.05)
-          AND location_postcode.country_code = country
-     ORDER BY ST_Distance(geom, location_postcode.geometry) LIMIT 1
-    INTO outcode;
+    -- Otherwise: be fully within the coverage area of a postcode
+    FOR location IN
+      SELECT postcode
+        FROM location_postcodes p
+       WHERE ST_Covers(p.geometry, geom)
+             AND p.country_code = country
+       ORDER BY osm_id is null, ST_Distance(p.centroid, geom)
+       LIMIT 1
+    LOOP
+        RETURN location.postcode;
+    END LOOP;
 
-    RETURN outcode;
+    RETURN NULL;
 END;
 $$
 LANGUAGE plpgsql STABLE PARALLEL SAFE;

lib-sql/indices.sql

@@ -48,9 +48,6 @@ CREATE INDEX IF NOT EXISTS idx_osmline_parent_place_id
 ---
 CREATE INDEX IF NOT EXISTS idx_osmline_parent_osm_id
   ON location_property_osmline USING BTREE (osm_id) {{db.tablespace.search_index}};
----
-CREATE INDEX IF NOT EXISTS idx_postcode_postcode
-  ON location_postcode USING BTREE (postcode) {{db.tablespace.search_index}};
 
 {% if drop %}
 ---
@@ -77,8 +74,8 @@ CREATE INDEX IF NOT EXISTS idx_postcode_postcode
     deferred BOOLEAN
    );
 ---
-  CREATE INDEX IF NOT EXISTS idx_location_postcode_parent_place_id
-    ON location_postcode USING BTREE (parent_place_id) {{db.tablespace.address_index}};
+  CREATE INDEX IF NOT EXISTS idx_location_postcodes_parent_place_id
+    ON location_postcodes USING BTREE (parent_place_id) {{db.tablespace.address_index}};
 {% endif %}
 
 -- Indices only needed for search.

lib-sql/table-triggers.sql

@@ -2,7 +2,7 @@
 --
 -- This file is part of Nominatim. (https://nominatim.org)
 --
--- Copyright (C) 2022 by the Nominatim developer community.
+-- Copyright (C) 2025 by the Nominatim developer community.
 -- For a full list of authors see the git log.
 
 -- insert creates the location tables, creates location indexes if indexed == true
@@ -25,5 +25,5 @@ CREATE TRIGGER place_before_delete BEFORE DELETE ON place
 CREATE TRIGGER place_before_insert BEFORE INSERT ON place
     FOR EACH ROW EXECUTE PROCEDURE place_insert();
 
-CREATE TRIGGER location_postcode_before_update BEFORE UPDATE ON location_postcode
+CREATE TRIGGER location_postcode_before_update BEFORE UPDATE ON location_postcodes
     FOR EACH ROW EXECUTE PROCEDURE postcode_update();

lib-sql/tables.sql

@@ -227,21 +227,29 @@ GRANT SELECT ON planet_osm_rels to "{{config.DATABASE_WEBUSER}}" ;
 GRANT SELECT on location_area to "{{config.DATABASE_WEBUSER}}" ;
 
 -- Table for synthetic postcodes.
-DROP TABLE IF EXISTS location_postcode;
-CREATE TABLE location_postcode (
-  place_id BIGINT,
+DROP TABLE IF EXISTS location_postcodes;
+CREATE TABLE location_postcodes (
+  place_id BIGINT NOT NULL,
   parent_place_id BIGINT,
+  osm_id BIGINT,
   rank_search SMALLINT,
-  rank_address SMALLINT,
   indexed_status SMALLINT,
   indexed_date TIMESTAMP,
   country_code varchar(2),
-  postcode TEXT,
-  geometry GEOMETRY(Geometry, 4326)
+  postcode TEXT NOT NULL,
+  centroid GEOMETRY(Geometry, 4326) NOT NULL,
+  geometry GEOMETRY(Geometry, 4326) NOT NULL
   );
-CREATE UNIQUE INDEX idx_postcode_id ON location_postcode USING BTREE (place_id) {{db.tablespace.search_index}};
-CREATE INDEX idx_postcode_geometry ON location_postcode USING GIST (geometry) {{db.tablespace.address_index}};
-GRANT SELECT ON location_postcode TO "{{config.DATABASE_WEBUSER}}" ;
+CREATE UNIQUE INDEX idx_location_postcodes_id ON location_postcodes
+  USING BTREE (place_id) {{db.tablespace.search_index}};
+CREATE INDEX idx_location_postcodes_geometry ON location_postcodes
+  USING GIST (geometry) {{db.tablespace.search_index}};
+CREATE INDEX IF NOT EXISTS idx_location_postcodes_postcode
+  ON location_postcodes USING BTREE (postcode, country_code)
+  {{db.tablespace.search_index}};
+CREATE INDEX IF NOT EXISTS idx_location_postcodes_osmid
+  ON location_postcodes USING BTREE (osm_id) {{db.tablespace.search_index}};
+GRANT SELECT ON location_postcodes TO "{{config.DATABASE_WEBUSER}}" ;
 
 -- Table to store location of entrance nodes
 DROP TABLE IF EXISTS placex_entrance;