lookup places for address tags for rank < 30

While previously the content of addr:* tags was only added
to the list of address search keywords, we now really look up
the matching place. This has the advantage that we pull in all
potential translations from the place, just like all the other
address terms that are looked up by neighbourhood search.

If no place can be found for a given name, the content of the
addr:* tag is still added to the search keywords as before.

sql/functions/ranking.sql

@@ -233,3 +233,50 @@ BEGIN
 END;
 $$
 LANGUAGE plpgsql IMMUTABLE;
+
+CREATE OR REPLACE FUNCTION get_addr_tag_rank(key TEXT, country TEXT,
+                                             OUT from_rank SMALLINT,
+                                             OUT to_rank SMALLINT,
+                                             OUT extent FLOAT)
+  AS $$
+DECLARE
+  ranks RECORD;
+BEGIN
+  from_rank := null;
+
+  FOR ranks IN
+    SELECT * FROM
+      (SELECT l.rank_search, l.rank_address FROM address_levels l
+        WHERE (l.country_code = country or l.country_code is NULL)
+               AND l.class = 'place' AND l.type = key
+        ORDER BY l.country_code LIMIT 1) r
+      WHERE rank_address > 0
+  LOOP
+    extent := reverse_place_diameter(ranks.rank_search);
+
+    IF ranks.rank_address <= 4 THEN
+        from_rank := 4;
+        to_rank := 4;
+    ELSEIF ranks.rank_address <= 9 THEN
+        from_rank := 5;
+        to_rank := 9;
+    ELSEIF ranks.rank_address <= 12 THEN
+        from_rank := 10;
+        to_rank := 12;
+    ELSEIF ranks.rank_address <= 16 THEN
+        from_rank := 13;
+        to_rank := 16;
+    ELSEIF ranks.rank_address <= 21 THEN
+        from_rank := 17;
+        to_rank := 21;
+    ELSEIF ranks.rank_address <= 24 THEN
+        from_rank := 22;
+        to_rank := 24;
+    ELSE
+        from_rank := 25;
+        to_rank := 25;
+    END IF;
+  END LOOP;
+END;
+$$
+LANGUAGE plpgsql IMMUTABLE;