Google App Engine NDB:如何存储文档结构? [英] Google App Engine NDB: How to store document structure?
问题描述
来自 App Engine NDB 文档:
From App Engine NDB documentation:
NDB API 在无模式对象中提供持久存储数据存储.它支持自动缓存、复杂的查询和原子交易.NDB 非常适合存储结构化数据记录.
The NDB API provides persistent storage in a schemaless object datastore. It supports automatic caching, sophisticated queries, and atomic transactions. NDB is well-suited to storing structured data records.
我想使用 NDB 创建如下结构,其中每个实例如下所示:
I want to create a structure like the following using NDB, where each instance looks like :
{
city: 'SFO'
date: '2013-01-27'
data: {
'keyword1': count1,
'keyword2': count2,
'keyword3': count3,
'keyword4': count4,
'keyword5': count5,
....
}
}
如何使用 NDB 在 Google App Engine (GAE) 中设计这样一个无架构的实体?
我是 GAE 的新手,不知道如何实现这一点
How can I design such a schema-less entity in Google App Engine(GAE) using NDB?
I am new to GAE and not sure how to achieve this
谢谢
推荐答案
如果您不需要查询数据中的属性,您可以使用@voscausa 提到的属性之一:
If you don't need to query for the attributes in data you can use one of the properties as mentioned by @voscausa:
Json 属性
class MyModel(ndb.Model):
city = ndb.StringProperty()
date = ndb.DateProperty()
data = ndb.JsonProperty()
my_model = MyModel(city="somewhere",
date=datetime.date.today(),
data={'keyword1': 3,
'keyword2': 5,
'keyword3': 1,})
结构化属性:
class Data(ndb.Model):
keyword = ndb.StringProperty()
count = ndb.IntegerProperty()
class MyModel(ndb.Model):
city = ndb.StringProperty()
date = ndb.DateProperty()
data = ndb.StructuredProperty(Data, repeated=True)
my_model = MyModel(city="somewhere",
date=datetime.date.today(),
data=[Data(keyword="keyword1", count=3),
Data(keyword="keyword2", count=5),
Data(keyword="keyword3", count=1)])
my_model.put()
这里的问题是过滤结构化属性.关键字的属性被视为并行数组.进行查询,例如:
The problem here is filtering for structured properties. The properties of Keyword are viewed as parallel arrays. Doing a query such as:
q = MyModel.query(MyModel.data.keyword=='keyword1',
MyModel.data.count > 4)
会错误地包含 my_model
.
https://developers.google.com/appengine/docs/python/ndb/queries#filtering_structured_properties
使用 expando 模型可以工作并允许您查询关键字:
Using an expando model would work and allow you to query for keywords:
class MyModel(ndb.Expando):
city = ndb.StringProperty()
date = ndb.DateProperty()
m = MyModel(city="Somewhere", date=datetime.date.today())
m.keyword1 = 3
m.keyword2 = 5
m.keyword3 = 1
m.put()
q = MyModel.query(ndb.GenericProperty('keyword1') > 2)
https://developers.google.com/appengine/docs/python/ndb/entities#expando
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