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Diffstat (limited to 'lib/sqlalchemy/ext/serializer.py')
| -rw-r--r-- | lib/sqlalchemy/ext/serializer.py | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/lib/sqlalchemy/ext/serializer.py b/lib/sqlalchemy/ext/serializer.py new file mode 100644 index 0000000..094b71b --- /dev/null +++ b/lib/sqlalchemy/ext/serializer.py @@ -0,0 +1,177 @@ +# ext/serializer.py +# Copyright (C) 2005-2022 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. + +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() |