@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] = []
+ can_create_by_id = False
+ _exists = True
def __init__(self, id_: BaseModelId | None) -> None:
if isinstance(id_, int) and id_ < 1:
msg = f'illegal {self.__class__.__name__} ID, must be >=1: {id_}'
raise HandledException(msg)
+ if isinstance(id_, str) and "" == id_:
+ msg = f'illegal {self.__class__.__name__} ID, must be non-empty'
+ 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
+ @property
+ def as_dict(self) -> dict[str, object]:
+ """Return self as (json.dumps-coompatible) dict."""
+ d: dict[str, object] = {'id': self.id_}
+ if len(self.to_save_versioned) > 0:
+ d['_versioned'] = {}
+ for k in self.to_save:
+ attr = getattr(self, k)
+ if hasattr(attr, 'as_dict'):
+ d[k] = attr.as_dict
+ d[k] = attr
+ for k in self.to_save_versioned:
+ attr = getattr(self, k)
+ assert isinstance(d['_versioned'], dict)
+ d['_versioned'][k] = attr.history
+ for r in self.to_save_relations:
+ attr_name = r[2]
+ d[attr_name] = [x.as_dict for x in getattr(self, attr_name)]
+ return d
+
+ # 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:
- """Empty class's cache."""
+ """Empty class's cache, and disappear all former inhabitants."""
+ # pylint: disable=protected-access
+ # (cause we remain within the class)
+ if hasattr(cls, 'cache_'):
+ to_disappear = list(cls.cache_.values())
+ for item in to_disappear:
+ item._disappear()
cls.cache_ = {}
@classmethod
cls.cache_ = d
return cls.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."""
+ cache = cls.get_cache()
+ if id_ in cache:
+ obj = cache[id_]
+ assert isinstance(obj, cls)
+ return obj
+ return None
+
def cache(self) -> None:
- """Update object in class's cache."""
+ """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 (sans relations), update DB cache with it."""
obj = cls(*row)
+ assert obj.id_ is not None
+ for attr_name in cls.to_save_versioned:
+ attr = getattr(obj, attr_name)
+ table_name = attr.table_name
+ for row_ in db_conn.row_where(table_name, 'parent', obj.id_):
+ attr.history_from_row(row_)
obj.cache()
return obj
@classmethod
- def by_id(cls, db_conn: DatabaseConnection,
- id_: BaseModelId | None,
- # pylint: disable=unused-argument
- create: bool = False) -> Self:
+ def by_id(cls, db_conn: DatabaseConnection, id_: BaseModelId) -> Self:
"""Retrieve by id_, on failure throw NotFoundException.
First try to get from cls.cache_, only then check DB; if found,
put into cache.
-
- If create=True, make anew (but do not cache yet).
"""
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
- if create:
- obj = cls(id_)
- return obj
raise NotFoundException(f'found no object of ID {id_}')
+ @classmethod
+ def by_id_or_create(cls, db_conn: DatabaseConnection,
+ id_: BaseModelId | None
+ ) -> Self:
+ """Wrapper around .by_id, creating (not caching/saving) if not find."""
+ if not cls.can_create_by_id:
+ raise HandledException('Class cannot .by_id_or_create.')
+ if id_ is None:
+ return cls(None)
+ try:
+ return cls.by_id(db_conn, id_)
+ except NotFoundException:
+ return cls(id_)
+
@classmethod
def all(cls: type[BaseModelInstance],
db_conn: DatabaseConnection) -> list[BaseModelInstance]:
return filtered
return items
+ # database writing
+
def save(self, db_conn: DatabaseConnection) -> None:
"""Write self to DB and cache and ensure .id_.
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