利用acts_as_ferret实现全文检索

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 %>

另一个高亮方案。

  def hilight(a,b)
    #a为要高亮的字符串，b为高亮部分，默认高亮后的样式为hilite
    highlight a,b, '\1'
  end


  

    <% @results.each do |result| %>
      
<%= hilight h(result.title),@query %>
      
<%= hilight simple_format(truncate(result.body,:length => 250)), @query %>
      
作者：<%= hilight h(result.author),@query %>  发表时间 <%= result.created_at_s %>
    <% 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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