look up different OSM types in placex separately

There are separate indexes on placex for the different OSM types.
PostgreSQL can only use these indexes if the type is fixed per query.

src/nominatim_api/lookup.py

@@ -201,22 +201,24 @@ async def find_in_placex(conn: SearchConnection, collector: Collector) -> bool:
                     t.c.geometry.ST_Expand(0).label('bbox'),
                     t.c.centroid)
 
-    osm_ids = [{'i': i, 'ot': p.osm_type, 'oi': p.osm_id, 'oc': p.osm_class or ''}
-               for i, p in collector.enumerate_free_osm_ids()]
-
-    if osm_ids:
-        oid_tab = sa.func.JsonArrayEach(sa.type_coerce(osm_ids, sa.JSON))\
-                    .table_valued(sa.column('value', type_=sa.JSON))
-        psql = sql.add_columns(oid_tab.c.value['i'].as_integer().label('_idx'))\
-                  .where(t.c.osm_type == oid_tab.c.value['ot'].as_string())\
-                  .where(t.c.osm_id == oid_tab.c.value['oi'].as_string().cast(sa.BigInteger))\
-                  .where(sa.or_(oid_tab.c.value['oc'].as_string() == '',
-                                oid_tab.c.value['oc'].as_string() == t.c.class_))\
-                  .order_by(t.c.class_)
-
-        if await collector.add_rows_from_sql(conn, psql, t.c.geometry,
-                                             nres.create_from_placex_row):
-            return True
+    for osm_type in ('N', 'W', 'R'):
+        osm_ids = [{'i': i, 'oi': p.osm_id, 'oc': p.osm_class or ''}
+                   for i, p in collector.enumerate_free_osm_ids()
+                   if p.osm_type == osm_type]
+
+        if osm_ids:
+            oid_tab = sa.func.JsonArrayEach(sa.type_coerce(osm_ids, sa.JSON))\
+                        .table_valued(sa.column('value', type_=sa.JSON))
+            psql = sql.add_columns(oid_tab.c.value['i'].as_integer().label('_idx'))\
+                      .where(t.c.osm_type == osm_type)\
+                      .where(t.c.osm_id == oid_tab.c.value['oi'].as_string().cast(sa.BigInteger))\
+                      .where(sa.or_(oid_tab.c.value['oc'].as_string() == '',
+                                    oid_tab.c.value['oc'].as_string() == t.c.class_))\
+                      .order_by(t.c.class_)
+
+            if await collector.add_rows_from_sql(conn, psql, t.c.geometry,
+                                                 nres.create_from_placex_row):
+                return True
 
     place_ids = [{'i': i, 'id': p.place_id}
                  for i, p in collector.enumerate_free_place_ids()]