如何限制实体的数量。谷歌应用引擎

Question

我只想制作 1 个 DailyPost 实体。但是当我同时发出两个请求时，就有两个 DailyPost 实体。

我该如何限制？

环境：

谷歌应用引擎

运行时：Python27

数据存储：ndb

def get_today():
  return datetime.datetime.combine(datetime.date.today(), datetime.time())

class DailyPost(ndb.Model):
  user = ndb.KeyProperty(kind=User)
  content = ndb.StringProperty()
  created = ndb.DateTimeProperty(auto_now_add=True)

class GetOrCreateHandler(webapp2.RequestHandler):
  def get(self):
    user = session.get_user() # user from session (pseudo code)
    post = DailyPost.query(DailyPost.created >= get_today(), 
                           DailyPost.user==user.key).get()
    if not post:
      # Delay to test. (or time.sleep)
      for i in range(30000):
        print 1
      post = DailyPost(content='some text..', user=user.key)
      post.put()

    self.response.write(post.content)

Answer 1

只需使用get_or_insert 方法将每天的唯一值作为键：

import datetime

class DailyPost(ndb.Model):
  user = ndb.KeyProperty(kind=User)
  content = ndb.StringProperty()
  #created = ndb.DateTimeProperty(auto_now_add=True)

class GetOrCreateHandler(webapp2.RequestHandler):
  def get(self):
    user = self.session.get_user() # user from session (pseudo code)
    _id = '%s.%s' % (user.id, datetime.date.today().strftime('%s'))
    DailyPost.get_or_insert(_id, user=user, content='bla')
    self.response.write(post.content)