Google Appengine NDB祖先与关键查询 [英] Google Appengine NDB ancestor vs key query

问题描述

我将一个实体的密钥存储为另一个实体的一个属性，以便将它们关联起来。在这个项目中，我们正在进行重构阶段，所以我正在考虑引进祖先。
这两种方法之间是否存在性能差异？如果我们引进祖先，我可能获得哪些优势？

  class Book（ndb.Model）：
 .. 。
 
 class Article（ndb.Model：
 book_key = ndb.KeyProperty（kind = Book，required = True）
 
 
 book_key = ndb。 Key（Book，12345）
  

第一个祖先查询方法 p>

  qry = Article.query（ancestor = book_key）
  

第二种简单的关键查询方式

  qry =文章.query（book_key = book_key）
  

解决方案

祖先查询将始终保持完全一致，另一方面，通过 book_key 查询不一定是一致的：您可能会发现最近的更改不会显示在该查询中。

另一方面，引入祖先对更新次数施加限制：每秒只能对任何实体gr进行一次更新oup（即祖先及其子女）。

这对你来说是一种权衡，哪一个在你的应用中更重要。 b

I am storing a key of an entity as a property of another in order to relate them. We are in a refactor stage at this point in the project so I was thinking about introducing ancestors. Is there a performance difference between the two approaches? Any given advantages that I might gain if we introduce ancestors?

class Book(ndb.Model):
  ...

class Article(ndb.Model:
  book_key = ndb.KeyProperty(kind=Book, required=True)


book_key =  ndb.Key("Book", 12345)

1st ancestor query approach

qry = Article.query(ancestor=book_key)

2st simple key query approach

qry = Article.query(book_key=book_key)

解决方案

The ancestor query will always be fully consistent. Querying by book_key, on the other hand, will not necessarily be consistent: you may find that recent changes will not be shown in that query.

On the other hand, introducing an ancestor imposes a limit on the number of updates: you can only do one update per second to any entity group (ie the ancestor and its children).

It's a trade-off for you as to which one is more important in your app.

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