Couple more questions
1. If I have the parent entity, how do get all the child entities?
2. If I have more fan out lists, so usernames is one, but now i have
emails and ipaddresses
is it more efficient to create different entity kinds or just add
another list to PageIndex?
i.e.
class PageIndex(db.Model):
usernames = db.StringListProperty(required=True)
emails = db.StringListProperty(required=True)
ipaddreses= db.StringListProperty(required=True)
or
class PageIndex(db.Model):
usernames = db.StringListProperty(required=True)
class PageEmailIndex(db.Model):
emails = db.StringListProperty(required=True)
class PageIpAddressIndex(db.Model):
ipaddreses= db.StringListProperty(required=True)
Thanks
Jon
On Aug 31, 11:19 pm, ogterran <jonathanh...@gmail.com> wrote:
> Thanks guys for all the responses.
> I checked out Brett's presentation and he talks about this exact issue
> on how to optimize using list properties
>
> So following the Brett's presentation, create 2 entitiy kinds.
> Page and PageIndex where Page is the parent of PageIndex (specify
> parent in PageIndex constructor)
>
> class Page(db.Model):
> pagekey= db.StringProperty(required=True)
>
> class PageIndex(db.Model):
> usernames = db.StringListProperty(required=True)
>
> indexes = db.GqlQuery("SELECT __key__ FROM MessageIndex "
> "WHERE usernames = :1", username)
> keys = [k.parent() for k in indexes]
> pages = db.get(keys)
>
> Since we are querying by key, it is 10x faster, and no unnecessary
> serialization.
> We can fan out by adding multiple PageIndex, if reaches 5000 max.
>
> Is this about right?
>
> Thanks
> Jon
>
> On Aug 31, 9:34 am, Jeff Schwartz <jefftschwa...@gmail.com> wrote:
>
>
>
> > A list property's size is limited to 5000.
>
> > If you only want to know if a user has visited a page, you can use the first
> > model & query it returning only keys to avoid list serialization issues. In
> > addition, key only queries are very fast.
>
> > Additionally, if your Page model's key had a string name that was the
> > pagecode then you could even use the key to identify the page. In other
> > words, you'd be materializing the view in the key of the model. This would
> > eliminate the need to serialize the entity entirely when it is used for
> > lookup.
>
> > Writing out the entity after having updated its list property is another
> > story all together as writes are subject to fail due to contention. To
> > reduce the odds of contention you can shard your model by a factor of 10 or
> > 20 to reduce but not eliminate the possibility of contention.
>
> > There are a number of Google IO videos on YouTube that you can watch which
> > cover these techniques.
>
> > Jeff
>
> > On Tue, Aug 31, 2010 at 5:22 AM, ogterran <jonathanh...@gmail.com> wrote:
> > > Hi,
>
> > > I have a choice to store the data two ways. Which way is more
> > > efficient when querying in BigTable?
>
> > > First way:
> > > class Page(db.Model):
> > > pagekey= db.StringProperty(required=True)
> > > usernames = db.StringListProperty(required=True)
>
> > > So all the users who visits the page, will be added to the username
> > > list
>
> > > Second way:
>
> > > class Page(db.Model):
> > > pagekey= db.StringProperty(required=True)
> > > username = db.StringProperty(required=True)
> > > All the users who visits the page will have its own row
>
> > > The query will be with both username and pagekey.
> > > There can be a lot of users.
> > > Is there a limit on theStringListsize?
> > > what are the advantages of each methods of storing data?
>
> > > Thanks
> > > Jon
>
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> > --
> > --
> > Jeff
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