谷歌App Engine數據存儲/ NoSQL示例與祖先查詢

Question

我很習慣於SQL，而不是App引擎數據存儲的NoSQL範例，所以我不得不編寫一段示例代碼來了解如何正確執行祖先查詢。以爲我會在這裏與你分享;也許這對某人很有意思。

Answer 1

#!/usr/bin/env python 
# -*- coding: utf-8 -*- 

import webapp2 
from google.appengine.ext.webapp.util import run_wsgi_app 
import logging 
from google.appengine.ext import db 

# MODELS 
class Child_model(db.Model): 
    name = db.StringProperty() 

class Parent_model(db.Model): 
    name = db.StringProperty() 

class Root_model(db.Model): 
    pass 


# MAIN 
class MainHandler(webapp2.RequestHandler): 
    def get(self, url): 
     if not Root_model.get_by_key_name("root"): 
      # Populate db on first run 
      self.populate() 

     logging.info("-- Get all enteties recursivly --") 
     root  = Root_model.get_by_key_name("root") 
     logging.info(" - %s", root) 

     parents  = Parent_model.all().ancestor(root) 

     # Recursivly 
     for p in parents: 
      logging.info(" -- %s" % p.name) 
      children = list(Child_model.all().ancestor(p)) 
      [logging.info(" --- %s" % c.name) for c in children] 

     # Shortcut 
     #children = Child_model.all().ancestor(root) 

     logging.info("-- Get all children for a parent --") 
     [logging.info(" -- %s" % c.name) for c in self.get_all_children_for_a_parent() ]  

     logging.info("-- Get some children for a parent --") 
     [logging.info(" -- %s" % c.name) for c in self.get_all_children_for_a_parent() if c.name == "Child num 0 with parent Parent num 0" or c.name == "Doesn't exist" ] 

     logging.info("-- Get parent for child --") 
     child = Child_model.all()[0] 
     logging.info("Child: %s" % child.name) 
     logging.info("Parent: %s" % child.parent().name) 

    def get_all_children_for_a_parent(self): 
     parent = Parent_model.all()[0] 
     logging.info(" - %s" % parent.name) 
     return Child_model().all().ancestor(parent) 


    def populate(self): 
     root = Root_model(key_name="root") 
     root.put() 

     parents = [] 
     for i in range(3): 
      parents.append(Parent_model(parent=root, name="Parent num %d" % i)) 
     db.put(parents) 

     import random 
     children = [] 
     for p in parents: 
      for i in range(random.randint(0,10)): 
       children.append(Child_model(parent=p, name="Child num %d with parent %s" % (i, p.name))) 
     db.put(children) 


app = webapp2.WSGIApplication([('/(.*)', MainHandler)], 
           debug=True) 
def main(): 
    run_wsgi_app(app) 

if __name__ == '__main__': 
    main()