+
+
+ async def get_property(self, name: str, cached: bool = True) -> str:
+ """ Get a property from Nominatim's property table.
+
+ Property values are normally cached so that they are only
+ retrieved from the database when they are queried for the
+ first time with this function. Set 'cached' to False to force
+ reading the property from the database.
+
+ Raises a ValueError if the property does not exist.
+ """
+ if name.startswith('DB:'):
+ raise ValueError(f"Illegal property value '{name}'.")
+
+ if cached and name in self._property_cache:
+ return cast(str, self._property_cache[name])
+
+ sql = sa.select(self.t.properties.c.value)\
+ .where(self.t.properties.c.property == name)
+ value = await self.connection.scalar(sql)
+
+ if value is None:
+ raise ValueError(f"Property '{name}' not found in database.")
+
+ self._property_cache[name] = cast(str, value)
+
+ return cast(str, value)
+
+
+ async def get_db_property(self, name: str) -> Any:
+ """ Get a setting from the database. At the moment, only
+ 'server_version', the version of the database software, can
+ be retrieved with this function.
+
+ Raises a ValueError if the property does not exist.
+ """
+ if name != 'server_version':
+ raise ValueError(f"DB setting '{name}' not found in database.")
+
+ return self._property_cache['DB:server_version']
+
+
+ async def get_class_table(self, cls: str, typ: str) -> Optional[SaFromClause]:
+ """ Lookup up if there is a classtype table for the given category
+ and return a SQLAlchemy table for it, if it exists.
+ """
+ if self._classtables is None:
+ res = await self.execute(sa.text("""SELECT tablename FROM pg_tables
+ WHERE tablename LIKE 'place_classtype_%'
+ """))
+ self._classtables = {r[0] for r in res}
+
+ tablename = f"place_classtype_{cls}_{typ}"
+
+ if tablename not in self._classtables:
+ return None
+
+ if tablename in self.t.meta.tables:
+ return self.t.meta.tables[tablename]
+
+ return sa.Table(tablename, self.t.meta,
+ sa.Column('place_id', sa.BigInteger),
+ sa.Column('centroid', Geometry))