U
|
¸ý°dÛ ã @ sÐ d Z ddlmZ ddlZddlZddlmZ ddlmZ ddlm Z ddl
|
m Z dd l m Z dd
|
lmZ dd lmZ dd lmZ dd lmZ ddddgZdd Ze d¡ZdddZejfddZdddZ dS )aN Serializer/Deserializer objects for usage with SQLAlchemy query structures,
|
allowing "contextual" deserialization.
|
|
.. legacy::
|
|
The serializer extension is **legacy** and should not be used for
|
new development.
|
|
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.
|
|
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