parent relationships
Martin Webb
Regards
Martin Webb
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Tim Hoffman
On Sep 21, 3:52 pm, Martin Webb <spydre...@yahoo.co.uk> wrote:
> Hi is it possible to add a entity of a model with a parent set to a key or
> another entity of the same model class.
> If so; does this make finding the
> siblings easier? If i load the parent or the sibling (child) is it easier to
> find the relating party(s).
within in children will mean you will get all children when doing a
straight ancestor query.
Remember you are also creating an entity group. So make sure you
don't create huge tree with a single parent ;-)
T
Martin Webb
Thinking about this i do need to store children with-in children so it sounds like i would have a problem getting the right level etc.
Am i correct.
Regards
Martin Webb
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From: Tim Hoffman <zute...@gmail.com>
To: Google App Engine <google-a...@googlegroups.com>
Sent: Tue, 21 September, 2010 9:34:23
Subject: [google-appengine] Re: parent relationships
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Tim Hoffman
If you many levels deep you definately need to look at a different
approach. (unless you do want them all in the same entity group.)
I have implemented non entity group relation ship with the following
basic approach. Here is just a bit of the code to give you some
ideas.
The whole lot can be found at. (http://code.google.com/p/bfg-pages/
source/browse/trunk/pages/models.py#406 you will see zope'isms in the
real code)
I plan to add some transaction management around this based on some of
Nick Johnsons articles.
class ContentishMixin(db.Model):
parent_ = db.ReferenceProperty(collection_name='children_')
path_elements_ = db.StringListProperty(default=[])
display_order = db.IntegerProperty(default=5)
def setParent(self,obj):
self.parent_ = obj
class FolderishMixin(db.Model):
children_keys = db.ListProperty(db.Key,default=[])
children_names = db.StringListProperty(str,default=[])
def addContent(self,obj,name):
if name in self.contentNames():
raise DuplicateName('duplicate name %s'%name)
self.children_keys.append(obj.key())
self.children_names.append(name)
obj.setParent(self)
obj.path_elements_ = self.path_elements
obj.put()
self.put()
def __getitem__(self,name):
name = unquote(name))
if name in self.children_names:
idx = self.children_names.index(name)
result = self._get(self.children_keys[idx])
result.__parent__ = self
return result
else:
raise KeyError(name)
def __contains__(self,name):
if name in self.children_names:
return True
else:
return False
There is no transactions around any of this so if you have multiple
concurrent addContent calls to the same folder you will run into
trouble.
T
On Sep 21, 4:52 pm, Martin Webb <spydre...@yahoo.co.uk> wrote:
> @tim
>
> If i do need to store children with in children - and if i have childs that
> could run to say one level but perhaps 500-1000 entities is it best to use a
> different aproach?
> Thinking about this i do need to store children with-in children so it sounds
> like i would have a problem getting the right level etc.
> Am i correct.
>
> Regards
>
> Martin Webb
> The information contained in this email is confidential and may contain
> proprietary information. It is meant solely for the intended recipient. Access
> to this email by anyone else is unauthorised. If you are not the intended
> recipient, any disclosure, copying, distribution or any action taken or omitted
> in reliance on this, is prohibited and may be unlawful. No liability or
> responsibility is accepted if information or data is, for whatever reason
> corrupted or does not reach its intended recipient. No warranty is given that
> this email is free of viruses. The views expressed in this email are, unless
> otherwise stated, those of the author
>
> ________________________________
Tim Hoffman
property of the children identifying depth from root.
The you can do a kindless ancestor query and filter by depth of parent
+ 1
T
On Sep 21, 4:52 pm, Martin Webb <spydre...@yahoo.co.uk> wrote:
> @tim
>
> If i do need to store children with in children - and if i have childs that
> could run to say one level but perhaps 500-1000 entities is it best to use a
> different aproach?
> Thinking about this i do need to store children with-in children so it sounds
> like i would have a problem getting the right level etc.
> Am i correct.
>
> Regards
>
> Martin Webb
> The information contained in this email is confidential and may contain
> proprietary information. It is meant solely for the intended recipient. Access
> to this email by anyone else is unauthorised. If you are not the intended
> recipient, any disclosure, copying, distribution or any action taken or omitted
> in reliance on this, is prohibited and may be unlawful. No liability or
> responsibility is accepted if information or data is, for whatever reason
> corrupted or does not reach its intended recipient. No warranty is given that
> this email is free of viruses. The views expressed in this email are, unless
> otherwise stated, those of the author
>
> ________________________________
Martin Webb
Regards
Martin Webb
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Martin Webb
Regards
Martin Webb
T. 01233 660879
F. 01233 640949
M. 07798946071
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Tim Hoffman
backref collection
In your case that will be the most efficient I think.
T
On Sep 21, 5:21 pm, Martin Webb <spydre...@yahoo.co.uk> wrote:
> Hi Tim. Just saw your last post. No i dont need something that complex. I dont
> need to sort them tho they could run into many thousands and beyond. I only need
> to load a say 10-100 at a time for display purposes. I did consider implementing
> as you have shown using the list property. But the issue of max 5000 entries
> plus the concurrency if multiple threads write made use a far less extragant
> model of just storing a domain key and then a key to a child as ref. i can then
> just fetch the childs by domain and then load them by key. It seems to work
> fine. Still pondering if it would be best to use a list property as you say ;-)
>
> Regards
>
> Martin Webb
>
> T. 01233 660879
> F. 01233 640949
> M. 07798946071
>
> The information contained in this email is confidential and may contain
> proprietary information. It is meant solely for the intended recipient. Access
> to this email by anyone else is unauthorised. If you are not the intended
> recipient, any disclosure, copying, distribution or any action taken or omitted
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>
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