利用acts_as_ferret实现全文检索
卢承弼
acts_as_ferret是在Rails中实现全文检索的插件，它的实现基于Ferret，Ferret是Apache Lucene的ruby接口。有关acts_as_ferret的介绍网上很多，教程也很多，是早期rails最重要的全文检索插件，不过要老外支持中文检索可谓是天荒地潭，javaeye中讲述中文支持的实现也不尽人意，而且都因年代久远，日益失去参考价值了。鉴此，我在放弃使用acts_as_ferret之前，详细介绍一下如何利用acts_as_ferret实现中文的全文检索吧，算是一个备案，或许未来会有用到它的时候。
独立安装gem
不要以插件方式安装，也不要unpack到你的项目下，原因不大清楚，但这是我血的教训总结出来的！
gem install ferret -v=0.11.5 --platform mswin32
gem install acts_as_ferret
gem install rmmseg
然后把C:/ruby/lib/ruby/gems/1.8/gems/ferret-0.11.5-x86-mswin32/ext目录下的ferret_ext.so复制到C:/ruby/lib/ruby/gems/1.8/gems/ferret-0.11.5-x86-mswin32/lib下！
关联gem
在你的项目的environment.rb添加
config.gem 'ferret'
config.gem 'rmmseg'
config.gem 'acts_as_ferret'
为模型添加索引支持
require 'rmmseg'
require 'rmmseg/ferret'
class Topic < ActiveRecord::Base
#……………………………………………………其他实现………………………………………………………………
#如果想重新建立索引，只需要删除对应的文件夹，并重启服务,也可以使用Model.rebuild_index方法
#=======================搜索部分=====================
acts_as_ferret({
:fields => {
:title => {
:store => :yes,
:boost=> 20 #设置权重
},
:body => {
:boost=> 1,
:store => :yes,
:term_vector => :with_positions_offsets
},
:author => {:store => :yes},
:created_at_s => {:index => :untokenized,:store => :yes},
:updated_at_s => {:index => :untokenized,:store => :yes}
},
:store_class_name=>true,
:analyzer => RMMSeg::Ferret::Analyzer.new
})
def created_at_s
created_at.to_s(:db)
end
def updated_at_s
updated_at.to_s(:db)
end
def body
first_post.body
end
#……………………………………………………其他实现………………………………………………………………
end
require 'rmmseg'
require 'rmmseg/ferret'
class Post < ActiveRecord::Base
#……………………………………………………其他实现………………………………………………………………
delegate :title, :to => :topic
#如果想重新建立索引，只需要删除对应的文件夹，并重启服务,也可以使用Model.rebuild_index方法
#=======================搜索部分=====================
acts_as_ferret({
:fields => {
:title => {
:store => :yes,
:boost=> 20 #设置权重
},
:body => {
:boost=> 1,
:store => :yes,
:term_vector => :with_positions_offsets
},
:author => {:store => :yes},
:created_at_s => {:index => :untokenized,:store => :yes},
:updated_at_s => {:index => :untokenized,:store => :yes}
},
:store_class_name => true,
:analyzer => RMMSeg::Ferret::Analyzer.new
})
def created_at_s
created_at.to_s(:db)
end
def updated_at_s
updated_at.to_s(:db)
end
#……………………………………………………其他实现………………………………………………………………
end
其中 :analyzer => RMMSeg::Ferret::Analyzer.new为我们添加了中文分词的能力。
建立Search模块
ruby script/generate controller search index
添加路由规则。
map.online '/seach', :controller => 'seach', :action => 'index'
修改search_controller。
class SearchController < ApplicationController
def index
@class = params[:class] || "topic"
@query = params[:query] || ''
unless @query.blank?
if @class == "topic"
@results = Topic.find_with_ferret @query
else
@results = Post.find_with_ferret @query
end
end
end
end
修改对应视图:
<% form_tag '/search', :method => :get ,:style => "margin-left:40%" do %>
<input type="radio" name="class" value = "topic" <%= @class == "topic"? 'checked="checked"':'' %>>仅主题贴
<input type="radio" name="class" value = "post" <%= @class == "post"? 'checked="checked"':'' %>>所有贴子<br>
<p>
<%= text_field_tag :query, @query %>
<%= submit_tag "搜索", :name => nil %>
</p>
<% end %>
<% if defined? @results %>
<style type="text/css">
.hilite{
color:#0042BD;
background:#F345CC;
}
</style>
<div id="search_result">
<% @results.each do |result| %>
<h3>
<%= result.highlight(@query,:field => :title,:pre_tag => "<span class='hilite'>",:post_tag => "</span>")%>
</h3>
<div><%= result.highlight(@query,:field => :body,:num_excerpts => 3,:excerpt_length => 250) %></div>
<p>作者：<%=result.author %> 发表时间 <%= result.created_at_s %></p>
<% end %>
</div>
<% end %>
分页
application_controller.rb添加
def pages_for(result,options = {})
page, per_page, total = (options[:page] || 1),(options[:per_page] || 30),(result.total_hits || 0)
page_total = page * per_page
index = (page.to_i - 1) * per_page
returning WillPaginate::Collection.new(page, per_page, total) do |pager|
pager.replace result[index,per_page]
end
end
修改控制器：
class SearchController < ApplicationController
def index
@class = params[:class] || "topic"
@query = params[:query] || ''
unless @query.blank?
if @class == "topic"
results = Topic.find_with_ferret @query
@results = pages_for(results ,:per_page => 3,:page=> (params[:page] || 1))
else
results = Post.find_with_ferret @query
@results = pages_for(results ,:per_page => 3,:page=> (params[:page] || 1))
end
end
end
end
对应视图的最下方添加一句(用到will_paginate插件)
<% form_tag '/search', :method => :get ,:style => "margin-left:40%" do %>
<input type="radio" name="class" value = "topic" <%= @class == "topic"? 'checked="checked"':'' %>>仅主题贴
<input type="radio" name="class" value = "post" <%= @class == "post"? 'checked="checked"':'' %>>所有贴子<br>
<p>
<%= text_field_tag :query, @query %>
<%= submit_tag "搜索", :name => nil %>
</p>
<% end %>
<% if defined? @results %>
<style type="text/css">
.hilite{
color:#0042BD;
background:#F345CC;
}
</style>
<div id="search_result">
<% @results.each do |result| %>
<h3>
<%= result.highlight(@query,:field => :title,:pre_tag => "<span class='hilite'>",:post_tag => "</span>")%>
</h3>
<div><%= result.highlight(@query,:field => :body,:num_excerpts => 3,:excerpt_length => 250) %></div>
<p>作者：<%=result.author %> 发表时间 <%= result.created_at_s %> 相关度 <= number_to_percentage result.ferret_score*100,:precision => 2 %><p>
<% end %>
</div>
<%= will_paginate @results ,:class => "non_ajax"%>
<% end %>
产品环境
- model里acts_as_ferret :remote=>true指定remote为true
- 把vendor/plugins/acts_as_ferret/config/目录下的ferret_server.yml copy到 config/下
- ruby script/runner vendor/plugins/acts_as_ferret/script/ferret_server -e production
一些有用的链接
http://www.pluitsolutions.com/2007/07/30/acts-as-ferret-drbserver-win32-service/
http://ferret.davebalmain.com/api/classes/Ferret/Index.html
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