mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-06-04 06:48:27 -04:00
Mike Bayer
5df1759e15
- inline default execution occurs for *all* non-PK columns unconditionally - preexecute only for non-executemany PK cols on PG, Oracle, etc. - new default docs
85 lines
2.3 KiB
Python
85 lines
2.3 KiB
Python
"""illustrates one way to use a custom pickler that is session-aware."""
|
|
|
|
from sqlalchemy import *
|
|
from sqlalchemy.orm import *
|
|
from sqlalchemy.orm.session import object_session
|
|
from cStringIO import StringIO
|
|
from pickle import Pickler, Unpickler
|
|
import threading
|
|
|
|
meta = MetaData('sqlite://')
|
|
meta.bind.echo = True
|
|
|
|
class MyExt(MapperExtension):
|
|
def populate_instance(self, mapper, selectcontext, row, instance, **flags):
|
|
MyPickler.sessions.current = selectcontext.session
|
|
return EXT_CONTINUE
|
|
def before_insert(self, mapper, connection, instance):
|
|
MyPickler.sessions.current = object_session(instance)
|
|
return EXT_CONTINUE
|
|
def before_update(self, mapper, connection, instance):
|
|
MyPickler.sessions.current = object_session(instance)
|
|
return EXT_CONTINUE
|
|
|
|
class MyPickler(object):
|
|
sessions = threading.local()
|
|
|
|
def persistent_id(self, obj):
|
|
if getattr(obj, "id", None) is None:
|
|
sess = MyPickler.sessions.current
|
|
newsess = create_session(bind=sess.connection(class_mapper(Bar)))
|
|
newsess.save(obj)
|
|
newsess.flush()
|
|
key = "%s:%s" % (type(obj).__name__, obj.id)
|
|
return key
|
|
|
|
def persistent_load(self, key):
|
|
name, ident = key.split(":")
|
|
sess = MyPickler.sessions.current
|
|
return sess.query(Bar).get(ident)
|
|
|
|
def dumps(self, graph, protocol):
|
|
src = StringIO()
|
|
pickler = Pickler(src)
|
|
pickler.persistent_id = self.persistent_id
|
|
pickler.dump(graph)
|
|
return src.getvalue()
|
|
|
|
def loads(self, data):
|
|
dst = StringIO(data)
|
|
unpickler = Unpickler(dst)
|
|
unpickler.persistent_load = self.persistent_load
|
|
return unpickler.load()
|
|
|
|
foo_table = Table('foo', meta,
|
|
Column('id', Integer, primary_key=True),
|
|
Column('bar', PickleType(pickler=MyPickler()), nullable=False))
|
|
|
|
bar_table = Table('bar', meta,
|
|
Column('id', Integer, primary_key=True),
|
|
Column('data', String(40)))
|
|
|
|
meta.create_all()
|
|
|
|
class Foo(object):
|
|
pass
|
|
|
|
class Bar(object):
|
|
def __init__(self, value):
|
|
self.data = value
|
|
|
|
mapper(Foo, foo_table, extension=MyExt())
|
|
mapper(Bar, bar_table)
|
|
|
|
sess = create_session()
|
|
f = Foo()
|
|
f.bar = Bar('some bar')
|
|
sess.save(f)
|
|
sess.flush()
|
|
sess.clear()
|
|
|
|
del MyPickler.sessions.current
|
|
|
|
f = sess.query(Foo).get(f.id)
|
|
assert f.bar.data == 'some bar'
|