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#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Models and helper functions for access to app's datastore metadata.
These entities cannot be created by users, but are created as results of
__namespace__, __kind__ and __property__ metadata queries such as
# Find all namespaces
q = db.GqlQuery("SELECT * FROM __namespace__")
for p in q.run():
print "namespace:", repr(p.namespace_name)
or
# Find all properties of A whose name starts with a lower-case letter
q = db.GqlQuery("SELECT __key__ from __property__ " +
"WHERE __key__ >= :1 AND __key__ < :2",
Property.key_for_property("A", "a"),
Property.key_for_property("A", chr(ord("z") + 1)))
for p in q.run():
print "%s: %s" % (Property.key_to_kind(p), Property.key_to_property(p))
or, using Query objects
# Find all kinds >= "a"
q = metadata.Kind().all()
q.filter("__key__ >=", metadata.Kind.key_for_kind("a"))
for p in q.run():
print "kind:", repr(p.kind_name)
"""
import os
if os.environ.get('APPENGINE_RUNTIME') == 'python27':
from google.appengine.api import datastore_types
from google.appengine.ext import db
else:
from google.appengine.api import datastore_types
from google.appengine.ext import db
[docs]class Namespace(BaseMetadata):
"""Model for __namespace__ metadata query results."""
KIND_NAME = '__namespace__'
EMPTY_NAMESPACE_ID = datastore_types._EMPTY_NAMESPACE_ID
@property
def namespace_name(self):
"""Return the namespace name specified by this entity's key."""
return self.key_to_namespace(self.key())
[docs] @classmethod
def key_for_namespace(cls, namespace):
"""Return the __namespace__ key for namespace.
Args:
namespace: namespace whose key is requested.
Returns:
The key for namespace.
"""
if namespace:
return db.Key.from_path(cls.KIND_NAME, namespace)
else:
return db.Key.from_path(cls.KIND_NAME, cls.EMPTY_NAMESPACE_ID)
[docs] @classmethod
def key_to_namespace(cls, key):
"""Return the namespace specified by a given __namespace__ key.
Args:
key: key whose name is requested.
Returns:
The namespace specified by key.
"""
return key.name() or ''
[docs]class Kind(BaseMetadata):
"""Model for __kind__ metadata query results."""
KIND_NAME = '__kind__'
@property
def kind_name(self):
"""Return the kind name specified by this entity's key."""
return self.key_to_kind(self.key())
[docs] @classmethod
def key_for_kind(cls, kind):
"""Return the __kind__ key for kind.
Args:
kind: kind whose key is requested.
Returns:
The key for kind.
"""
return db.Key.from_path(cls.KIND_NAME, kind)
[docs] @classmethod
def key_to_kind(cls, key):
"""Return the kind specified by a given __kind__ key.
Args:
key: key whose name is requested.
Returns:
The kind specified by key.
"""
return key.name()
[docs]class Property(BaseMetadata):
"""Model for __property__ metadata query results."""
KIND_NAME = '__property__'
@property
def property_name(self):
"""Return the property name specified by this entity's key."""
return self.key_to_property(self.key())
@property
def kind_name(self):
"""Return the kind name specified by this entity's key."""
return self.key_to_kind(self.key())
property_representation = db.StringListProperty()
[docs] @classmethod
def key_for_kind(cls, kind):
"""Return the __property__ key for kind.
Args:
kind: kind whose key is requested.
Returns:
The parent key for __property__ keys of kind.
"""
return db.Key.from_path(Kind.KIND_NAME, kind)
[docs] @classmethod
def key_for_property(cls, kind, property):
"""Return the __property__ key for property of kind.
Args:
kind: kind whose key is requested.
property: property whose key is requested.
Returns:
The key for property of kind.
"""
return db.Key.from_path(Kind.KIND_NAME, kind, Property.KIND_NAME, property)
[docs] @classmethod
def key_to_kind(cls, key):
"""Return the kind specified by a given __property__ key.
Args:
key: key whose kind name is requested.
Returns:
The kind specified by key.
"""
if key.kind() == Kind.KIND_NAME:
return key.name()
else:
return key.parent().name()
[docs] @classmethod
def key_to_property(cls, key):
"""Return the property specified by a given __property__ key.
Args:
key: key whose property name is requested.
Returns:
property specified by key, or None if the key specified only a kind.
"""
if key.kind() == Kind.KIND_NAME:
return None
else:
return key.name()
[docs]class EntityGroup(BaseMetadata):
"""Model for __entity_group__ metadata (available in HR datastore only).
This metadata contains a numeric __version__ property that is guaranteed
to increase on every change to the entity group. The version may increase
even in the absence of user-visible changes to the entity group. The
__entity_group__ entity may not exist None if the entity group was never
written to.
"""
KIND_NAME = '__entity_group__'
ID = 1
version = db.IntegerProperty(name='__version__')
[docs] @classmethod
def key_for_entity(cls, entity_or_key):
"""Return the metadata key for the entity group containing entity_or_key.
Use this key to get() the __entity_group__ metadata entity for the
entity group containing entity_or_key.
Args:
entity_or_key: a key or entity whose __entity_group__ key you want.
Returns:
The __entity_group__ key for the entity group containing entity_or_key.
"""
if isinstance(entity_or_key, db.Model):
key = entity_or_key.key()
else:
key = entity_or_key
while key.parent():
key = key.parent()
return db.Key.from_path(cls.KIND_NAME, cls.ID, parent=key)
[docs]def get_namespaces(start=None, end=None):
"""Return all namespaces in the specified range.
Args:
start: only return namespaces >= start if start is not None.
end: only return namespaces < end if end is not None.
Returns:
A list of namespace names between the (optional) start and end values.
"""
q = Namespace.all()
if start is not None:
q.filter('__key__ >=', Namespace.key_for_namespace(start))
if end is not None:
q.filter('__key__ <', Namespace.key_for_namespace(end))
return [x.namespace_name for x in q.run()]
[docs]def get_kinds(start=None, end=None):
"""Return all kinds in the specified range.
Args:
start: only return kinds >= start if start is not None.
end: only return kinds < end if end is not None.
Returns:
A list of kind names between the (optional) start and end values.
"""
q = Kind.all()
if start is not None and start != '':
q.filter('__key__ >=', Kind.key_for_kind(start))
if end is not None:
if end == '':
return []
q.filter('__key__ <', Kind.key_for_kind(end))
return [x.kind_name for x in q.run()]
[docs]def get_properties_of_kind(kind, start=None, end=None):
"""Return all properties of kind in the specified range.
NOTE: This function does not return unindexed properties.
Args:
kind: name of kind whose properties you want.
start: only return properties >= start if start is not None.
end: only return properties < end if end is not None.
Returns:
A list of property names of kind between the (optional) start and end
values.
"""
q = Property.all(keys_only=True)
q.ancestor(Property.key_for_kind(kind))
if start is not None and start != '':
q.filter('__key__ >=', Property.key_for_property(kind, start))
if end is not None:
if end == '':
return []
q.filter('__key__ <', Property.key_for_property(kind, end))
return [Property.key_to_property(x) for x in q.run()]
[docs]def get_representations_of_kind(kind, start=None, end=None):
"""Return all representations of properties of kind in the specified range.
NOTE: This function does not return unindexed properties.
Args:
kind: name of kind whose properties you want.
start: only return properties >= start if start is not None.
end: only return properties < end if end is not None.
Returns:
A dictionary mapping property names to its list of representations.
"""
q = Property.all()
q.ancestor(Property.key_for_kind(kind))
if start is not None and start != '':
q.filter('__key__ >=', Property.key_for_property(kind, start))
if end is not None:
if end == '':
return {}
q.filter('__key__ <', Property.key_for_property(kind, end))
result = {}
for property in q.run():
result[property.property_name] = property.property_representation
return result
[docs]def get_entity_group_version(entity_or_key):
"""Return the version of the entity group containing entity_or_key.
Args:
entity_or_key: a key or entity whose version you want.
Returns: The version of the entity group containing entity_or_key. This
version is guaranteed to increase on every change to the entity
group. The version may increase even in the absence of user-visible
changes to the entity group. May return None if the entity group was
never written to.
On non-HR datatores, this function returns None.
"""
eg = db.get(EntityGroup.key_for_entity(entity_or_key))
if eg:
return eg.version
else:
return None
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2023-04-04 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2023-04-04 UTC."],[],[]]
