Google App Engine Datastore/NoSQL 예 (조상 쿼리 포함)

Question

저는 App Engine Datastore의 NoSQL 패러다임이 아닌 SQL에 익숙하므로 조상 쿼리를 올바르게 수행하는 방법을 이해하기 위해 예제 코드를 작성해야했습니다. 내가 너와 여기서 그것을 나눌 줄 알았다. 어쩌면 누군가에게 흥미로울 것입니다.

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()