export centroid to tokenizer

May come in handy when developping sanitizers for an area smaller
than country size.

lib-sql/functions/placex_triggers.sql

@@ -16,7 +16,9 @@ CREATE TYPE prepare_update_info AS (
   country_code TEXT,
   class TEXT,
   type TEXT,
-  linked_place_id BIGINT
+  linked_place_id BIGINT,
+  centroid_x float,
+  centroid_y float
 );
 
 -- Retrieve the data needed by the indexer for updating the place.
@@ -71,6 +73,8 @@ BEGIN
   result.type := p.type;
   result.country_code := p.country_code;
   result.rank_address := p.rank_address;
+  result.centroid_x := ST_X(p.centroid);
+  result.centroid_y := ST_Y(p.centroid);
 
   -- Names of linked places need to be merged in, so search for a linkable
   -- place already here.

nominatim/data/place_info.py

@@ -8,7 +8,7 @@
 Wrapper around place information the indexer gets from the database and hands to
 the tokenizer.
 """
-from typing import Optional, Mapping, Any
+from typing import Optional, Mapping, Any, Tuple
 
 class PlaceInfo:
     """ This data class contains all information the tokenizer can access
@@ -62,6 +62,15 @@ class PlaceInfo:
         return self._info.get('rank_address', 0)
 
 
+    @property
+    def centroid(self) -> Optional[Tuple[float, float]]:
+        """ A center point of the place in WGS84. May be None when the
+            geometry of the place is unknown.
+        """
+        x, y = self._info.get('centroid_x'), self._info.get('centroid_y')
+        return None if x is None or y is None else (x, y)
+
+
     def is_a(self, key: str, value: str) -> bool:
         """ Set to True when the place's primary tag corresponds to the given
             key and value.