由StructuredProperty的属性进行NDB排序 [英] NDB ordering by property of StructuredProperty

问题描述

假设我在另一个模型类中使用 ndb.Model 类作为 StructuredProperty ：

  class CommonExtraData（ndb.Model）：
 count = ndb.IntegerProperty（required = True）
 
 class MyObject（ndb.Model）：
 name = ndb.StringProperty（required = True）
 extra = ndb.StructuredProperty（CommonExtraData，required = True）
  
 
 $ b 
然后我可以做这样的查询： 
 
 
  MyObject.query（）。order（-MyObject.extra.count）
  
我可以在文档中找不到示例，而我的开发环境目前还不能正常工作，这是因为我努力从旧API重构到NDB。
     解决方案刚刚做了一些实验，看起来很有效。你应该能够按照你写出来的方式完成它。
 
 
 
在实验中，我发现了一个应该注意的怪癖 - 如果你使用重复属性，它似乎排序仅限重复财产的第一个实例。例如，如果您的重复属性具有[CommonExtraData（count = 5），CommonExtraData（count = 1）]，另一个具有[CommonExtraData（count = 7），CommonExtraData（count = 2）]，则它将按如下排序： p> 
 
 [CommonExtraData（count = 7），CommonExtraData（count = 2）] 
 [CommonExtraData（count = 5），CommonExtraData（count = 1）] 
 
Say I have an ndb.Model class that I want to use as a StructuredProperty on another model class:
class CommonExtraData(ndb.Model):
    count = ndb.IntegerProperty(required=True)

class MyObject(ndb.Model):
    name = ndb.StringProperty(required=True)
    extra = ndb.StructuredProperty(CommonExtraData, required=True)
Could I then do a query like this:
MyObject.query().order(-MyObject.extra.count)
I can't find an example in the docs, and my dev environment is not currently working due to my endeavors of refactoring from the old API to NDB.
解决方案
Just did a bit of experimentation and it appears to be working. You should be able to do it exact as you wrote out.

In experimenting, I found one quirk that should be noted - if you use repeated property, it appears to sort on the first instance of the repeated property only. For example, if your repeated property had [CommonExtraData(count=5), CommonExtraData(count=1)] and another had [CommonExtraData(count=7), CommonExtraData(count=2)], it would sort like this:

[CommonExtraData(count=7), CommonExtraData(count=2)]
[CommonExtraData(count=5), CommonExtraData(count=1)]

                        
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