来自 App Engine NDB documentation :
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 创建如下所示的结构,其中每个实例如下所示:
{
city: 'SFO'
date: '2013-01-27'
data: {
'keyword1': count1,
'keyword2': count2,
'keyword3': count3,
'keyword4': count4,
'keyword5': count5,
....
}
}
我如何使用 NDB 在 Google App Engine(GAE) 中设计这样一个无模式的实体?
我是 GAE 的新手,不确定如何实现这一点
谢谢
最佳答案
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:
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。进行如下查询:
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 模型会起作用并允许您查询关键字:
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
关于python - 谷歌应用引擎 NDB : How to store document structure?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/14544834/