Assuming you have
try:
from gluon.contrib.gql import * # if running on Google App
Engine
except:
db=SQLDB('sqlite://storage.db') # if not, use SQLite or
other DB - Used by T2
datastoretype = 'SQL'
else:
db=GQLDB() # connect to Googl
datastoretype = 'GAE'
# So now, db is the GAE db
# To use those Collections in the Reference properites, you need to
insert NATIVE GAE references,
# so you need to somehow find the GAE entity instance reference given
a web2py sql row
# Here is the 'Stargate / wormhole' code which takes you from web2py
back down into the native GAE Datastore alternate universe:
# So if you have a web2py table name 'ChildTable':
web2pyChildTableClass = db.ChildTable # gives the web2py Table
class
theNativeGAEChildTableClass = web2pyChildTableClass._tableobj #
magic... into GAE
# ================================================================
# Now do a native GAE query to find the native GAE instance so it
# can be put into the Reference collection:
nativeGAE ChildTableQuery = theNativeGAEChildTableClass.all()
nativeGAEChildTableQuery.filter('id =', 25) # get for id = 25
nativeresults = nativeGAEChildTableQuery.fetch(limit=1)
myGAENativeChild = nativeresults[0]
# Now myGAENativeChild can be inserted into the native GAE Reference
collection
- Dave Lypka
On Jun 26, 5:48 am, Carles Gonzalez <carle...@gmail.com> wrote:
> Very interesting, i didn't know about collection_name and the associated
> query.
>
> You are shedding some light on doing relationships the GAE way.
>
> Thanks again.
>
>
>
> On Sat, Jun 26, 2010 at 8:52 AM, dlypka <dly...@gmail.com> wrote:
>
> > For starters:
>
> > Refer to
> >http://arbingersys.blogspot.com/2008/04/google-app-engine-one-to-many...
>
> > And Here is the posting about using native GAE properties
>
> >http://groups.google.com/group/web2py/browse_thread/thread/7112ef7dee...
>
> > So for example you would do
>
> > from gluon.contrib.gql import gae
> > :
> > :
> > db.define_table('ChildItem',
> > # NOTE: web2py provides the 'id'
> > column automatically
> > db.Field('idParentFolder','reference
> > MyParent'),
> > db.Field('name','text'),
> > db.Field('gaeParentInstance',
> > gae.ReferenceProperty(MyParent,
> > required=False,
> > collection_name='linksFromChildItemToParent')))
>
> > )
>
> > and define the parent class in a similar fashion.
>
> > It is also necessary to add some plumbing to find and track the native
> > GAE references
> > which lie underneath the web2py sql objects because the native refs
> > have to be
> > put into the collections.
>
> > I'll provide more details in some followup posts.
>
> > On Jun 25, 2:48 pm, Carles <carle...@gmail.com> wrote:
> >> Thanks a lot Dave.
>
> >> There isn't a deadline, tale your time :)
>
> >> Carles
>
> >> El 25/06/2010, a las 20:42, dlypka <dly...@gmail.com> escribió:
>
> >> > OK will do - please give me a few days...
>
> >> > On Jun 24, 8:43 pm, Carles Gonzalez <carle...@gmail.com> wrote:
> >> >> Not to be annoying, but can you post an example?
>
> >> >> Just to organize the things in my head...
>
> >> >> Thanks again.
>
> >> >> On Fri, Jun 25, 2010 at 2:41 AM, Carles Gonzalez <carle...@gmail.com>
> >> >> wrote:
> >> >>> Very interesting!
>
> >> >>> I'll try tomorrow.
>
> >> >>> Thanks a lot, Dave.
>
> >> >>> On Fri, Jun 25, 2010 at 1:21 AM, dlypka <dly...@gmail.com> wrote:
> >> >>>> I've done a parent - to - many child GAE / web2py implementation using
> >> >>>> SelfReference fields (or you can use Reference as well) using the
> >> >>>> technique for adding native GAE fields into a web2py table definition.
>
> >> >>>> It gives fantastic retrieval performance because GAE automatically
> >> >>>> adds the link from the child back into the parent's reference list
> >> >>>> at the time you create each child. When you later query for the
> >> >>>> parent, voila GAE retrieves all the child entities along with it in
> >> >>>> one backend call!
>
> >> >>>> Hopefully this technique is relevant to your application.
>
> >> >>>> I also develop some other tricks for inheriting native GAE classes
> >> >>>> into your web2py model, though
> >> >>>> this is less attractive perhaps now that GAE native properties can be
> >> >>>> directly declared in web2py tables.
>
> >> >>>> - Dave Lypka.
>
> >> >>>> On Jun 21, 10:25 am, Carles Gonzalez <carle...@gmail.com> wrote:
> >> >>>>> Hi,
>
> >> >>>>> I have developed some applications in web2py, and 2 are running
> >> >>>>> currently in gae, but now i have serious problem.
>
> >> >>>>> My current project is a social application, and when i design
> >> >>>>> (example) the tables to make an user follow the actions other user
> >> >>>>> (twitter like) I find that many-to-many relationships in app-engine
> >> >>>>> are not easily supported.
>
> >> >>>>> From my understanding using the tools present in web2py right i would
> >> >>>>> need to do a lot of processing in memory, an that would hurt
> >> >>>>> performance greatly.
>
> >> >>>>> The pattern proposed by app store developers uses lists and "parent"
> >> >>>>> relationship:
>
> >> >>>>> class Message(db.Model):
> >> >>>>> sender = db.StringProperty()
> >> >>>>> body = db.TextProperty()
>
> >> >>>>> class MessageIndex(db.Model):
> >> >>>>> receivers = db.StringListProperty()
>
> >> >>>>> indexes = MessageIndex.all(keys_only = True).filter('receivers = ',
> >> >>>>> user_id)
> >> >>>>> keys = [k.parent() for k in indexes)
> >> >>>>> messages = db.get(keys)
>
> >> >>>>> For using that pattern in web2py I would need a method for specifying
> >> >>>>> the parent of a model instance. Can I specify that relationship using
> >> >>>>> any method I don't know? If not, would it be hard to implement?
>
> >> >>>>> Thanks in advance!
