无法在Google App Engine中使用过滤器查询数据存储（Python）

Question

我不太确定哪里出了问题。我正在尝试在一个数据存储中查询一个简单的字符串，但查询的结果总是为空。

这是我的模型文件(models.py)：

from google.appengine.ext import db
from google.appengine.api import datastore_types

class Post(db.Model):
    author = db.TextProperty()
    title = db.TextProperty()
    slug = db.TextProperty()
    #slug = str()

这是我的主程序文件(main.py)：

import wsgiref.handlers
from google.appengine.ext import webapp
from google.appengine.ext.webapp import util
from models import *
import logging
import os

os.environ['DJANGO_SETTINGS_MODULE'] = 'settings'
from google.appengine.dist import use_library
use_library('django', '1.2')
from django.template.defaultfilters import slugify


class MainHandler(webapp.RequestHandler):
    def get(self):

        # store some random posts
        title1 = "Road to the perfect car wax."
        title2 = "10 ways to get a perfect car wax."
        slug1 = slugify(title1)
        slug2 = slugify(title2)

        post1 = Post(author="Tom Tomton", title=title1, slug=str(slug1))
        post2 = Post(author="John Jonston", title=title2, slug=str(slug2))

        posts = list()
        posts.append(post1)
        posts.append(post2)
        db.put(posts)

        # use filter to find a post
        q = Post.all()
        q.filter("slug =",str(slug1))
        #q.filter("slug =","road-to-the-perfect-car-wax")
        result = q.fetch(1)[0] # empty!
        logging.info("result: %s" % result) 

        self.response.out.write('<p class="item">%s, %s</p>' % (result.author, result.title))


application = webapp.WSGIApplication([('/.*', MainHandler)], debug=True)


def main():
    wsgiref.handlers.CGIHandler().run(application)
    #util.run_wsgi_app(application)

if __name__ == '__main__':
    main()

但是在数据存储查看器中，输出清楚地显示这个字符串确实存在：

2   1   None    Tom Tomton  road-to-the-perfect-car-wax     Road to the perfect car wax.
2   2   None    John Jonston    10-ways-to-get-a-perfect-car-wax    10 ways to get a perfect car wax.

我尝试过使用1.5.5和1.5.0版本的应用引擎。

Answer 1

TextProperty 是一种文本属性，它们不会被索引，也就是说你不能通过它们来进行筛选。如果你需要能够被索引的属性，建议使用 StringProperty。