Sorry, but I don't use Java. I will give you the Python version, it's pretty
straight forward. As I said before, any improvements in my design or code
will be welcome =)
class User(Model):
# for easy of use, i will consider user_id as the key name of the entity
name, email, etc
num_of_followers = IntegerProperty(default=0)
class FollowerInfo(Model):
master = StringProperty() I've used String property to store the key_name,
but you can use KeyProperty if you prefer. This will be the super-star
posting new things
followers = ListProperty() # or arrays, the other thing MiuMeet proposed
full = BooleanProperty() # whether we can store more followers here or not
class Post(Model):
content, author, etc...
class PostNotify(Model):
# key name/key_id of the entity will be key_name/key_id of the post
users = ListProperty()
*User X follows User Y:*
# Check if there is already a FollowerInfo model, and hasn't got more than
100 followers or so.
follower = Query(..).filter('full = ', False).filter('master',
UserHere).fetch(1)
if not follower: # create one if we need it
follower = FollowerInfo(parent=UserHere, followers=[,])
# Add follower, check if the info is full too
follower.followers.append(FollowerUserHere)
if len(follower.followers) >= 100:
follower.full = True
follower.put() # save
# maybe this must be in a transaction?
user.num_of_followers += 1
user.put()
*
*
*User X doesn't follow User Y anymore:*
*
*
follower = Query(...).filter('followers = ', FollowerUserHere).fetch(1)
follower.followers.delete(FollowerUserHere)
# check if the model was full, now it will have one empty slot more
if follower.full and len(follower.followers) < 100:
follower.full = False
follower.put() # save
# again, maybe this must be in a transaction?
user.num_of_followers -= 1
user.put()
*List followers:*
*
*
# I fetch one of the following info models. It may be null (no followers),
one model(1-100 followers). If the user has more following info models
(100-infinite), it will return only one of them.
follower = Query(..).filter('master =', UserHere).fetch(1)
if follower:
# List here the follower.followers
*Post:*
*
*
if UserHere.num_of_followers > 100:
taskqueue....() # add new task to process it offline, too much followers!
# process it inline here otherwise (same code as in the task)
TASK:
- Get each one of the FollowerInfo models for the user
- Create a PostNotify with the key_name/key_id of the post for each 4500 or
so, followers.
- Save all the PostNotify entities
*List notifications:*
*
*
# I run a keys-only query, finding the first 50 (or whatever you want
notifications for this user).
# As you don't have to deserialize the list (keys-only), you'll never incur
in that perfomance cost. The key has all the info you need (the post
key_name/key_id, it's exactly the same)
notifications = Query(entity=PostNotify, keys_only=True).filter('users =',
CurrentUserHere).fetch(50)
ids = []
for notification in notifications
ids.append(notification.key_name)
# Now you have all the posts
posts = db.get(ids)
2011/8/3 Bruno Sandivilli <[email protected]>
> So, if an user X adds and User Y, the user Y will become an ancestor of X ?
> And if the user Y adds the user W too, so user X will have two
> ancestors(???) ? Any code snippets will be greatful.
> Thanks again, for the help guys.
>
>
> 2011/8/2 MiuMeet Support <[email protected]>
>
>> By the way, have a look at:
>> http://devblog.miumeet.com/2011/08/much-more-efficient-implementation-of.html
>>
>> It's much more efficient than db.ListProperty(int)
>>
>> Cheers,
>> -Andrin
>>
>>
>> On Thu, Jul 28, 2011 at 6:17 PM, Pascal Voitot Dev <
>> [email protected]> wrote:
>>
>>> good idea also :)
>>>
>>>
>>> On Wed, Jul 27, 2011 at 7:17 PM, Ernesto Oltra
>>> <[email protected]>wrote:
>>>
>>>> And for followers, you could too shard the lists. You can have several
>>>> entities, each with, about 100 results or so (or 1000, or 2000, I prefer
>>>> 100
>>>> for easy of serializing/deserializing). All these would have the user as
>>>> ancestor. When listing, take only one entity, deserializing its lists (only
>>>> 100 results) and show some of them. When listing all, you can use cursors
>>>> and some tricks to have the job done (job = paging =) )
>>>>
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