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Edit File: serializer.py
# ext/serializer.py # Copyright (C) 2005-2023 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: https://www.opensource.org/licenses/mit-license.php """Serializer/Deserializer objects for usage with SQLAlchemy query structures, allowing "contextual" deserialization. Any SQLAlchemy query structure, either based on sqlalchemy.sql.* or sqlalchemy.orm.* can be used. The mappers, Tables, Columns, Session etc. which are referenced by the structure are not persisted in serialized form, but are instead re-associated with the query structure when it is deserialized. .. warning:: The serializer extension uses pickle to serialize and deserialize objects, so the same security consideration mentioned in the `python documentation <https://docs.python.org/3/library/pickle.html>`_ apply. Usage is nearly the same as that of the standard Python pickle module:: from sqlalchemy.ext.serializer import loads, dumps metadata = MetaData(bind=some_engine) Session = scoped_session(sessionmaker()) # ... define mappers query = Session.query(MyClass). filter(MyClass.somedata=='foo').order_by(MyClass.sortkey) # pickle the query serialized = dumps(query) # unpickle. Pass in metadata + scoped_session query2 = loads(serialized, metadata, Session) print query2.all() Similar restrictions as when using raw pickle apply; mapped classes must be themselves be pickleable, meaning they are importable from a module-level namespace. The serializer module is only appropriate for query structures. It is not needed for: * instances of user-defined classes. These contain no references to engines, sessions or expression constructs in the typical case and can be serialized directly. * Table metadata that is to be loaded entirely from the serialized structure (i.e. is not already declared in the application). Regular pickle.loads()/dumps() can be used to fully dump any ``MetaData`` object, typically one which was reflected from an existing database at some previous point in time. The serializer module is specifically for the opposite case, where the Table metadata is already present in memory. """ import re from .. import Column from .. import Table from ..engine import Engine from ..orm import class_mapper from ..orm.interfaces import MapperProperty from ..orm.mapper import Mapper from ..orm.session import Session from ..util import b64decode from ..util import b64encode from ..util import byte_buffer from ..util import pickle from ..util import text_type __all__ = ["Serializer", "Deserializer", "dumps", "loads"] def Serializer(*args, **kw): pickler = pickle.Pickler(*args, **kw) def persistent_id(obj): # print "serializing:", repr(obj) if isinstance(obj, Mapper) and not obj.non_primary: id_ = "mapper:" + b64encode(pickle.dumps(obj.class_)) elif isinstance(obj, MapperProperty) and not obj.parent.non_primary: id_ = ( "mapperprop:" + b64encode(pickle.dumps(obj.parent.class_)) + ":" + obj.key ) elif isinstance(obj, Table): if "parententity" in obj._annotations: id_ = "mapper_selectable:" + b64encode( pickle.dumps(obj._annotations["parententity"].class_) ) else: id_ = "table:" + text_type(obj.key) elif isinstance(obj, Column) and isinstance(obj.table, Table): id_ = ( "column:" + text_type(obj.table.key) + ":" + text_type(obj.key) ) elif isinstance(obj, Session): id_ = "session:" elif isinstance(obj, Engine): id_ = "engine:" else: return None return id_ pickler.persistent_id = persistent_id return pickler our_ids = re.compile( r"(mapperprop|mapper|mapper_selectable|table|column|" r"session|attribute|engine):(.*)" ) def Deserializer(file, metadata=None, scoped_session=None, engine=None): unpickler = pickle.Unpickler(file) def get_engine(): if engine: return engine elif scoped_session and scoped_session().bind: return scoped_session().bind elif metadata and metadata.bind: return metadata.bind else: return None def persistent_load(id_): m = our_ids.match(text_type(id_)) if not m: return None else: type_, args = m.group(1, 2) if type_ == "attribute": key, clsarg = args.split(":") cls = pickle.loads(b64decode(clsarg)) return getattr(cls, key) elif type_ == "mapper": cls = pickle.loads(b64decode(args)) return class_mapper(cls) elif type_ == "mapper_selectable": cls = pickle.loads(b64decode(args)) return class_mapper(cls).__clause_element__() elif type_ == "mapperprop": mapper, keyname = args.split(":") cls = pickle.loads(b64decode(mapper)) return class_mapper(cls).attrs[keyname] elif type_ == "table": return metadata.tables[args] elif type_ == "column": table, colname = args.split(":") return metadata.tables[table].c[colname] elif type_ == "session": return scoped_session() elif type_ == "engine": return get_engine() else: raise Exception("Unknown token: %s" % type_) unpickler.persistent_load = persistent_load return unpickler def dumps(obj, protocol=pickle.HIGHEST_PROTOCOL): buf = byte_buffer() pickler = Serializer(buf, protocol) pickler.dump(obj) return buf.getvalue() def loads(data, metadata=None, scoped_session=None, engine=None): buf = byte_buffer(data) unpickler = Deserializer(buf, metadata, scoped_session, engine) return unpickler.load()