python - 由于 cursor() 方法中 "IN filter"的限制，使用游标进行分页查询会导致错误...应该有什么替代方法？

Question

我正在使用以下模型开发一个类似 Twitter 的微博系统:

class Member(db.Model):    
    user = db.UserProperty(required=True)
    follower_count = db.IntegerProperty(default=0) # members following you    
    following_count = db.IntegerProperty(default=0) # members you are following

class NewsItem(db.Model):    
    text = db.StringProperty(required=True)
    posted_by = db.ReferenceProperty(reference_class=Member,required=True,collection_name="posted_items")
    posted_on = db.DateTimeProperty(auto_now_add=True)
    status = db.IntegerProperty(default=1) # 0: deleted

class Follow(db.Model):    
    member = db.ReferenceProperty(reference_class=Member,required=True,collection_name="followings")    
    followed_member = db.ReferenceProperty(reference_class=Member,required=True,collection_name="followers")    
    added_on = db.DateTimeProperty(auto_now_add=True) 

在此模型结构中，我使用以下代码检索当前用户关注的成员的消息:

follow_log_list = Follow.gql('WHERE member = :1 ', member)
followed_member_list = []
for follow_log in follow_log_list:
    followed_member_list.append(follow_log.followed_member)

query = NewsItem.all()
query.filter('posted_by IN', followed_member_list)
query.filter('status =', 1)
query.order('-posted_on')
query.with_cursor(cursor)   
newsList = query.fetch(10)  

template_values['cursor'] = query.cursor()

调用 query.cursor() 方法时出现以下错误:

"No cursor available for a MultiQuery (queries using "IN" or "!=" operators)"

这是正常的，因为在游标的文档中，此限制已明确说明为:

http://code.google.com/appengine/docs/python/datastore/queries.html

“您不能将游标用于使用 IN 或 != 过滤运算符的查询。”

获取关注成员的帖子的替代方法是什么？

谢谢，

编辑:发布的消息按其状态过滤并按发布日期排序...但示例未在此处显示，我已经更改...

Answer 1

一种快速而讨厌的方式...

下载此 pagintor.py将其导入您的项目。

然后你可以为分页做这样的事情

    from paginator import Paginator, InvalidPage, EmptyPage
     model = Member.all().fetch(100)
     paginator = Paginator(model,5)

                if(self.request.GET):
                    page = int(self.request.GET.get('page', '1'))
                    if(page is not None):
                        try:
                            page = int(self.request.GET.get('page', '1'))
                        except ValueError:
                            page = 1

                        # If page request (9999) is out of range, deliver last page of results.
                        try:
                            paginator = paginator.page(page)
                        except (EmptyPage, InvalidPage):
                            paginator = paginator.page(paginator.num_pages)
    return self.response.out.write( template.render(path+'.html',{'paginator':paginator}))


#In templates

{% if paginator.object_list %}

{% for values in paginator.object_list %}

#do your tasks

{% endfor %}
<div  align="right" class="pagination" >
        {% if paginator.has_previous %}
            <a  id="previous" href="{{ paginator.previous_page_number }}">Previous</a>
        {% else %}
         <span class="page-nulled" >
            Previous
        </span>
        {% endif %}

        <span class="current" id="pagenum" title="{{ paginator.number }}">
            &nbsp;&nbsp;&nbsp;Page {{ paginator.number }} of {{paginator.paginator.num_pages }}&nbsp;&nbsp;&nbsp;
        </span>

        {% if paginator.has_next %}
            <a  id="next" href="{{ paginator.next_page_number }}"> Next </a>
            {% else %}
         <span class="page-nulled" >
            Next 
        </span>
        {% endif %}

</div>

点击 next 或 previous 时，获取 href val() 并作为 get 变量传递给 url，例如 http://someurl?page= .

更多引用 here