App Engine数据存储区非规范化:主实体或非规范化实体中的索引属性?

考虑博客数据建模的经典示例，其中我们有一个具有许多属性的Blog实体，并且我们希望在页面中列出最新的博客.

Consider the classic example of blog data modelling, where we have a Blog entity with many properties, and we want to list the latest blogs in a page.

将BlogPost实体反规范化为BlogPostSummary实体(将在列表视图中显示)是有意义的，从而避免了获取和反序列化许多不需要的属性.

It makes sense to denormalize the BlogPost entity into a BlogPostSummary entity which will be shown in the list view, avoiding fetching and deserializing many unwanted properties.

class BlogPost(db.Model):
  title = db.StringProperty()
  content = db.TextProperty()
  created = db.DateProperty()
  ...

class BlogPostSummary(db.Model):
  title = db.StringProperty()
  content_excerpt = db.TextProperty()

问题是:哪个实体应拥有索引属性?有3个选项:

The question is: which entity should hold the indexed properties? There are 3 options:

• 优点:
  • 轻松查询两个实体.
  • Pros:
    • Easy query on both entities.
    • 维护非规范化索引非常昂贵.
    • 优点:
      • 主要实体中的索引属性更加安全，因为非规范化实体被视为冗余.
      • Pros:
        • Indexing properties in the main entity is more safe, as the denormalized entity is treated as redundancy.
        • 查询列表视图将需要两次往返数据存储:对BlogPost实体进行一次单键查询，然后对BlogPostSummary进行批量获取.
        • Querying the list view will need a double roundtrip to datastore: One to key-only query for BlogPost entities, followed by a batch get for BlogPostSummary.
        • 优点:
          • 可以通过单个查询轻松构建列表视图.
          • Pros:
            • The list view can be easily built by a single query.
            • 这些属性无法再查询主要实体.
            • 当非规范化实体是主要实体的子代时，索引会占用更多空间.

            哪个选项会更好?还有其他选择吗?

            Which option would work better? Are there other options?

            在选项2中进行数据存储的双向往返是否会出现问题?

            Would the double round trip to datastore in option 2 be a problem?