继续扩展博客功能

• 自定义模板标签和filter，也就是自定义一个小函数用来处理
• 给站点增加站点地图和post feed
• 用PostgreSQL实现全文搜索

自定义template tag

• simple_tag: 处理数据并且返回字符串
• inclusion_tag: 处理数据返回渲染后的页面（其实也是字符串）

simple_tag

from django import template
from ..models import Post

register = template.Library()


@register.simple_tag
def total_posts():
    return Post.published.count()

@register.simple_tag(name='my_tag')

{% load blog_tags %}

<p>This is my blog. I've written {% total_posts %} posts so far.</p>

include_tag

@register.inclusion_tag('blog/post/latest_posts.html')
def show_latest_posts(count=5):
    latest_posts = Post.published.order_by('-publish')[:count]
    return {'latest_posts': latest_posts}

<ul>
{% for post in latest_posts %}
<li>
<a href="{{ post.get_absolute_url }}">{{ post.title }}</a>
</li>
{% endfor %}
</ul>

<h3>Latest Posts</h3>
{% show_latest_posts %}

灵活使用自定义标签

@register.simple_tag
def get_most_commented_posts(count=5):
    return Post.published.annotate(total_comments=Count('comments')).order_by('-total_comments')[:count]

<h3>Most commented posts</h3>
{% get_most_commented_posts as most_commented_posts %}
<ul>
{% for post in most_commented_posts %}
<li>
<a href="{{ post.get_absolute_url }}">{{ post.title }}</a>
</li>
{% endfor %}
</ul>

自定义filter

pip install Markdown==2.6.11

from django.utils.safestring import mark_safe
import markdown

@register.filter(name='markdown')
def markdown_format(text):
    return mark_safe(markdown.markdown(text))

This is a post formatted with markdown
--------------------------------------
*This is emphasized* and **this is more emphasized**.
Here is a list:

* One
* Two
* Three

And a [link to the Django website](https://www.djangoproject.com/)

站点地图

SITE_ID = 1
# Application definition
INSTALLED_APPS = [
# ...
'django.contrib.sites',
'django.contrib.sitemaps',

from django.contrib.sitemaps import Sitemap
from .models import Post


class PostSitemap(Sitemap):
    changefreq = 'weekly'
    priority = 0.9

    def items(self):
        return Post.published.all()

    def lastmod(self, obj):
        return obj.updated

from django.contrib.sitemaps.views import sitemap
from blog.sitemaps import PostSitemap
sitemaps = {
    'posts': PostSitemap,
}
urlpatterns = [
    path('admin/', admin.site.urls),
    path('blog/', include('blog.urls', namespace='blog')),
    path('sitemap.xml', sitemap, {'sitemaps': sitemaps},
    name='django.contrib.sitemaps.views.sitemap')
]

为博客的文章建立feeds

from django.contrib.syndication.views import Feed
from django.template.defaultfilters import truncatewords
from .models import Post


class LastestPostFeed(Feed):
    title = 'My blog'
    link = '/blog/'
    description = 'New posts of my blog.'

    def items(self):
        return Post.published.all()[:5]

    def item_title(self, item):
        return item.title

    def item_description(self, item):
        return truncatewords(item.body, 30)

• title 就是 RSS 的<title>元素
• link 就是 RSS 的<link>元素
• description 就是 RSS 的<description>元素
• items()方法表示包含在feed中的数据对象
• item_title()方法表示对于每个数据对象的标题显示什么
• item_description()表示每个对象的描述显示什么，这里用了内置的截取30个单词的功能。

path('feed/', LastestPostFeed(), name='post_feed'),

<p><a href='{% url "blog:post_feed" %}'>Subscribe to my RSS feed</a></p>

为博客增加全文搜索功能

Post.objects.filter(body__contains='framework')

安装PostgreSQL数据库

sudo apt-get install libpq-dev python-dev
sudo apt-get install postgresql postgresql-contrib

pip install psycopg2==2.7.4

PostgreSQL数据库的一些基本配置

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'blog',
        'USER': 'blog',
        'PASSWORD': '*******',
    }
}

开始进行简单的搜索

from blog.models import Post
po = Post.objects.filter(body__search='time')

同时在多个字段进行检索

from django.contrib.postgres.search import SearchVector
from blog.models import Post

Post.objects.annotate(search=SearchVector('title','body'),).filter(search='poem')

建立搜索功能

class SearchForm(forms.Form):
    query = forms.CharField()

from django.contrib.postgres.search import SearchVector
from .forms import EmailPostForm, CommentForm, SearchForm

def post_search(request):
    form = SearchForm()
    query = None
    results = []
    if 'query' in request.GET:
        form = SearchForm(request.GET)
        if form.is_valid():
            query = form.cleaned_data['query']
            results = Post.objects.annotate(search=SearchVector('title', 'slug', 'body'), ).filter(search=query)
    return render(request, 'blog/post/search.html', {'query': query, "form": form, 'results': results})

{% extends 'blog/base.html' %}

{% block title %}
Search
{% endblock %}

{% block content %}
{% if query %}
    <h1>Post containing {{ query }}</h1>
    <h3>
    {% with results.count as total_results %}
        Found {{ total_results }} result{{ total_results|pluralize }}
    {% endwith %}
    </h3>
    {% for post in results %}
        <h4>
            <a href="{{ post.get_absolute_url }}">{{ post.title }}</a>
        </h4>
        {{ post.body|truncatewords:5 }}
    {% empty %}
        <p>There are no results for your query.</p>
    {% endfor %}
    <p><a href="{% url 'blog:post_search' %}">Search again</a></p>
{% else %}
    <h1>Search for posts</h1>
    <form action="." method="get">
    {{ form.as_p }}
        <input type="submit" value="Search">
    </form>
{% endif %}
{% endblock %}

path('search/', views.post_search, name='post_search'),

搜索优化和排名

# 导入新的SearchQuery和SearchRank
from django.contrib.postgres.search import SearchVector, SearchQuery, SearchRank
# 把原来查询功能那一行删除，改成几个分离的变量和新的查询
    search_vector = SearchVector('title', 'body')
    search_query = SearchQuery(query)
    results = Post.objects.annotate(
                search=search_vector,
                rank=SearchRank(search_vector, search_query)
            ).filter(search=search_query).order_by('-rank')

搜索权重

search_vector = SearchVector('title', weight='A') + SearchVector('body', weight='B')
results = Post.objects.annotate(
                search=search_vector,
                rank=SearchRank(search_vector, search_query)
            ).filter(rank__gte=0.33).order_by('-rank')

三元相似性搜索

from django.contrib.postgres.search import TrigramSimilarity
results = Post.objects.annotate(
              similarity=TrigramSimilarity('title',query),
              ).filter(similarity__gte=0.1).order_by('-similarity')

使用其他全文搜索引擎

总结

• 建立自定义的tag，分为simple_tag和可以渲染一段HTML的include_tag
• 建立自定义的filter，非常强大，用这个方式很轻松的就让博客支持了markdown语法
• 通过django内置功能建立站点地图，生成一个XML文件供搜索引擎爬虫读取
• 通过django内置功能建立RSS feed供RSS阅读器进行读取
• 配置第三方数据库
• PostgreSQL的安装和简单使用，pgAdmin图形化界面操作数据库
• 引入Django中专门为PostgreSQL服务的一系列组件进行搜索
• 直接用field__search进行简单搜索
• 建立搜索向量对多个字段进行搜索
• 按照搜索匹配次数的排名返回搜索结果
• 分离搜索向量，每个字段建立权重，按权重返回搜索结果
• 为PostgreSQL建立pg_trgm扩展，然后使用内置的三元相似性搜索
• Haystack引入其他全文搜索引擎