GAE 查询计数器 (+1000)
如何将此查询计数器实现到现有类中？主要目的是我有超过 3000 条记录的成员数据存储模型。我只想计算它的总记录，并在应用程序引擎食谱中找到了这个：
def query_counter (q, cursor=None, limit=500):
if cursor:
q.with_cursor (cursor)
count = q.count (limit=limit)
if count == limit:
return count + query_counter (q, q.cursor (), limit=limit)
return count
我现有的模型是：
class Members(search.SearchableModel):
group = db.ListProperty(db.Key,default=[])
email = db.EmailProperty()
name = db.TextProperty()
gender = db.StringProperty()
此外，我想计算通过列表引用加入特定组的成员。它还可能包含超过 1000 条记录。
有人有用于此目的的 query.cursor 的经验吗？
How to implement this query counter into existing class? The main purpose is i have datastore model of members with more than 3000 records. I just want to count its total record, and found this on app engine cookbook:
def query_counter (q, cursor=None, limit=500):
if cursor:
q.with_cursor (cursor)
count = q.count (limit=limit)
if count == limit:
return count + query_counter (q, q.cursor (), limit=limit)
return count
My existing model is:
class Members(search.SearchableModel):
group = db.ListProperty(db.Key,default=[])
email = db.EmailProperty()
name = db.TextProperty()
gender = db.StringProperty()
Further i want to count members that join certain group with list reference. It might content more than 1000 records also.
Anyone have experience with query.cursor for this purpose?
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要查找所有成员，您可以像这样使用它：
但是，您可能会发现它运行缓慢，因为它进行了大量数据存储调用。
更快的方法是拥有一个单独的模型类（例如 MembersCount），并在其中维护计数（即创建成员时加 1，删除成员时减 1）。
如果您经常创建和删除成员，则可能需要创建分片计数器才能获得良好的性能 - 请参阅此处了解详细信息：
http://code.google.com/appengine/articles/sharding_counters.html
要计算某个群组中的成员数量，您可以执行以下操作：
如果您预计有大量成员组中的成员数量，您还可以通过使用由组分片的计数器模型来更有效地做到这一点。
To find all members you would use it like this:
However, you may find that this runs slowly, because it's making a lot of datastore calls.
A faster way would be to have a separate model class (eg MembersCount), and maintain the count in there (ie add 1 when you create a member, subtract 1 when you delete a member).
If you are creating and deleting members frequently you may need to create a sharded counter in order to get good performance - see here for details:
http://code.google.com/appengine/articles/sharding_counters.html
To count members in a certain group, you could do something like this:
If you expect to have large numbers of members in a group, you could also do that more efficiently by using a counter model which is sharded by the group.