diff options
| -rw-r--r-- | examples/dynamic_dict/dynamic_dict.py | 53 |
1 files changed, 33 insertions, 20 deletions
diff --git a/examples/dynamic_dict/dynamic_dict.py b/examples/dynamic_dict/dynamic_dict.py index 3846c2994..f58c19c00 100644 --- a/examples/dynamic_dict/dynamic_dict.py +++ b/examples/dynamic_dict/dynamic_dict.py @@ -2,23 +2,21 @@ that dictionary operations (assuming simple string keys) can operate upon a large
collection without loading the full collection at once.
-This is something that may eventually be added as a feature to dynamic_loader() itself.
-
Similar approaches could be taken towards sets and dictionaries with non-string keys
although the hash policy of the members would need to be distilled into a filter() criterion.
"""
-class MyProxyDict(object):
+class ProxyDict(object):
def __init__(self, parent, collection_name, childclass, keyname):
self.parent = parent
self.collection_name = collection_name
self.childclass = childclass
self.keyname = keyname
-
+
+ @property
def collection(self):
return getattr(self.parent, self.collection_name)
- collection = property(collection)
def keys(self):
descriptor = getattr(self.childclass, self.keyname)
@@ -41,43 +39,58 @@ class MyProxyDict(object): from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine, Column, Integer, String, ForeignKey
-from sqlalchemy.orm import sessionmaker, dynamic_loader
+from sqlalchemy.orm import sessionmaker, relation
-Base = declarative_base(engine=create_engine('sqlite://'))
+engine=create_engine('sqlite://', echo=True)
+Base = declarative_base(engine)
-class MyParent(Base):
+class Parent(Base):
__tablename__ = 'parent'
id = Column(Integer, primary_key=True)
name = Column(String(50))
- _collection = dynamic_loader("MyChild", cascade="all, delete-orphan")
+ _collection = relation("Child", lazy="dynamic", cascade="all, delete-orphan")
+ @property
def child_map(self):
- return MyProxyDict(self, '_collection', MyChild, 'key')
- child_map = property(child_map)
+ return ProxyDict(self, '_collection', Child, 'key')
-class MyChild(Base):
+class Child(Base):
__tablename__ = 'child'
id = Column(Integer, primary_key=True)
key = Column(String(50))
parent_id = Column(Integer, ForeignKey('parent.id'))
+ def __repr__(self):
+ return "Child(key=%r)" % self.key
Base.metadata.create_all()
sess = sessionmaker()()
-p1 = MyParent(name='p1')
+p1 = Parent(name='p1')
sess.add(p1)
-p1.child_map['k1'] = k1 = MyChild(key='k1')
-p1.child_map['k2'] = k2 = MyChild(key='k2')
+print "\n---------begin setting nodes, autoflush occurs\n"
+p1.child_map['k1'] = Child(key='k1')
+p1.child_map['k2'] = Child(key='k2')
+
+# this will autoflush the current map.
+# ['k1', 'k2']
+print "\n---------print keys - flushes first\n"
+print p1.child_map.keys()
-assert p1.child_map.keys() == ['k1', 'k2']
+# k1
+print "\n---------print 'k1' node\n"
+print p1.child_map['k1']
-assert p1.child_map['k1'] is k1
+print "\n---------update 'k2' node - must find existing, and replace\n"
+p1.child_map['k2'] = Child(key='k2')
-p1.child_map['k2'] = k2b = MyChild(key='k2')
-assert p1.child_map['k2'] is k2b
+print "\n---------print 'k2' key - flushes first\n"
+# k2
+print p1.child_map['k2']
-assert sess.query(MyChild).all() == [k1, k2b]
+print "\n---------print all child nodes\n"
+# [k1, k2b]
+print sess.query(Child).all()
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