@property
def _user_version(self) -> int:
"""Get DB user_version."""
- # pylint: disable=protected-access
- # (since we remain within class)
- return self.__class__._get_version_of_db(self.path)
+ return self._get_version_of_db(self.path)
def _validate_schema(self) -> None:
"""Compare found schema with what's stored at PATH_DB_SCHEMA."""
id_: None | BaseModelId
cache_: dict[BaseModelId, Self]
to_search: list[str] = []
+ _exists = True
def __init__(self, id_: BaseModelId | None) -> None:
if isinstance(id_, int) and id_ < 1:
raise HandledException(msg)
self.id_ = id_
+ def __hash__(self) -> int:
+ hashable = [self.id_] + [getattr(self, name) for name in self.to_save]
+ for definition in self.to_save_relations:
+ attr = getattr(self, definition[2])
+ hashable += [tuple(rel.id_ for rel in attr)]
+ for name in self.to_save_versioned:
+ hashable += [hash(getattr(self, name))]
+ return hash(tuple(hashable))
+
def __eq__(self, other: object) -> bool:
if not isinstance(other, self.__class__):
return False
- to_hash_me = tuple([self.id_] +
- [getattr(self, name) for name in self.to_save])
- to_hash_other = tuple([other.id_] +
- [getattr(other, name) for name in other.to_save])
- return hash(to_hash_me) == hash(to_hash_other)
+ return hash(self) == hash(other)
def __lt__(self, other: Any) -> bool:
if not isinstance(other, self.__class__):
assert isinstance(other.id_, int)
return self.id_ < other.id_
- @classmethod
- def get_cached(cls: type[BaseModelInstance],
- id_: BaseModelId) -> BaseModelInstance | None:
- """Get object of id_ from class's cache, or None if not found."""
- # pylint: disable=consider-iterating-dictionary
- cache = cls.get_cache()
- if id_ in cache.keys():
- obj = cache[id_]
- assert isinstance(obj, cls)
- return obj
- return None
+ # cache management
+ # (we primarily use the cache to ensure we work on the same object in
+ # memory no matter where and how we retrieve it, e.g. we don't want
+ # .by_id() calls to create a new object each time, but rather a pointer
+ # to the one already instantiated)
+
+ def __getattribute__(self, name: str) -> Any:
+ """Ensure fail if ._disappear() was called, except to check ._exists"""
+ if name != '_exists' and not super().__getattribute__('_exists'):
+ raise HandledException('Object does not exist.')
+ return super().__getattribute__(name)
+
+ def _disappear(self) -> None:
+ """Invalidate object, make future use raise exceptions."""
+ assert self.id_ is not None
+ if self._get_cached(self.id_):
+ self._uncache()
+ to_kill = list(self.__dict__.keys())
+ for attr in to_kill:
+ delattr(self, attr)
+ self._exists = False
@classmethod
def empty_cache(cls) -> None:
cls.cache_ = d
return cls.cache_
- def cache(self) -> None:
- """Update object in class's cache."""
+ @classmethod
+ def _get_cached(cls: type[BaseModelInstance],
+ id_: BaseModelId) -> BaseModelInstance | None:
+ """Get object of id_ from class's cache, or None if not found."""
+ # pylint: disable=consider-iterating-dictionary
+ cache = cls.get_cache()
+ if id_ in cache.keys():
+ obj = cache[id_]
+ assert isinstance(obj, cls)
+ return obj
+ return None
+
+ def _cache(self) -> None:
+ """Update object in class's cache.
+
+ Also calls ._disappear if cache holds older reference to object of same
+ ID, but different memory address, to avoid doing anything with
+ dangling leftovers.
+ """
if self.id_ is None:
raise HandledException('Cannot cache object without ID.')
- cache = self.__class__.get_cache()
+ cache = self.get_cache()
+ old_cached = self._get_cached(self.id_)
+ if old_cached and id(old_cached) != id(self):
+ # pylint: disable=protected-access
+ # (cause we remain within the class)
+ old_cached._disappear()
cache[self.id_] = self
- def uncache(self) -> None:
+ def _uncache(self) -> None:
"""Remove self from cache."""
if self.id_ is None:
raise HandledException('Cannot un-cache object without ID.')
- cache = self.__class__.get_cache()
+ cache = self.get_cache()
del cache[self.id_]
+ # object retrieval and generation
+
@classmethod
def from_table_row(cls: type[BaseModelInstance],
# pylint: disable=unused-argument
db_conn: DatabaseConnection,
row: Row | list[Any]) -> BaseModelInstance:
- """Make from DB row, write to DB cache."""
+ """Make from DB row, update DB cache with it."""
obj = cls(*row)
- obj.cache()
+ obj._cache()
return obj
@classmethod
"""
obj = None
if id_ is not None:
- obj = cls.get_cached(id_)
+ obj = cls._get_cached(id_)
if not obj:
for row in db_conn.row_where(cls.table_name, 'id', id_):
obj = cls.from_table_row(db_conn, row)
- obj.cache()
break
if obj:
return obj
return filtered
return items
+ # database writing
+
def save(self, db_conn: DatabaseConnection) -> None:
"""Write self to DB and cache and ensure .id_.
values)
if not isinstance(self.id_, str):
self.id_ = cursor.lastrowid # type: ignore[assignment]
- self.cache()
+ self._cache()
for attr_name in self.to_save_versioned:
getattr(self, attr_name).save(db_conn)
for table, column, attr_name, key_index in self.to_save_relations:
def remove(self, db_conn: DatabaseConnection) -> None:
"""Remove from DB and cache, including dependencies."""
- if self.id_ is None or self.__class__.get_cached(self.id_) is None:
+ if self.id_ is None or self._get_cached(self.id_) is None:
raise HandledException('cannot remove unsaved item')
for attr_name in self.to_save_versioned:
getattr(self, attr_name).remove(db_conn)
for table, column, attr_name, _ in self.to_save_relations:
db_conn.delete_where(table, column, self.id_)
- self.uncache()
+ self._uncache()
db_conn.delete_where(self.table_name, 'id', self.id_)
+ self._disappear()
projects / plomtask / blobdiff