全文搜尋 Sphinx on Rails

Update(2009/3/31): 除了 ultrasphinx 之外，還有一套 Ruby library 是 thinking sphinx 目前已經是最被推薦的 Rails 套件，我也推薦改使用 thinking sphinx，peepcode 有出它的 PDF。

雖然在 Ruby/Rails 圈比較常聽到 Ferret，不過這隻雪貂的穩定度一直為人所詬病。我在 survey Rails 全文搜尋方案的時候，看到另一個有 Rails plugin 支援的開放源碼全文搜尋引擎 Sphinx，搭配的 Rails plugin 叫做 Ultrasphinx。

Sphinx 的特點在於它直接存取 MySQL (或PostgreSQL)，完全獨立於 Rails app。它不像 acts_as_ferret 和 acts_as_solr 使用 rails callback 來做新資料的索引動作，而是設定 crontab 定期跑 indexer (如每半小時)，大大提高了 search daemon 穩定度(反之亦然)，也不太有索引資料損壞的問題(在講ferret?)。目前看到的評價也都是穩穩穩高效能，用過就不想再用 Ferret 了。Ultrasphinx 的作者也有 benchmark 數據可供佐證。

安裝第一步是去 Sphinx 官方網站下載並 compile

wget
tar xvf sphinx-.tar.gz
cd sphinx-
./configure && make && sudo make install

安裝 chronic gem

sudo gem install chronic

安裝 ultrasphinx plugin:

script/plugin install svn://rubyforge.org/var/svn/fauna/ultrasphinx/trunk

如果要分頁功能，ultrasphinx 也有支援 will_paginate plugin。

 script/plugin install svn:://errtheblog.com/svn/plugins/will_paginate

裝好之後就來設定

mkdir config/ultrasphinx
cp vendor/plugin/ultrasphinx/examples/default.base config/ultrasphinx/

設定檔的部份我就直接大贈送給各位(記得改path)，包括支援中文搜尋，這個答案在官網討論區有。

indexer
{
  # Indexer running options
  mem_limit = 256M 
}

searchd
{
  address = 0.0.0.0
  port = 3312
  log = log/searchd.log
  query_log = log/query.log
  read_timeout = 5
  max_children = 300
  pid_file = log/searchd.pid
  max_matches = 100000
}

client
{
  # Client options
  # Name of the Aspell dictionary (two letters max)
  dictionary_name = ap
  # How your application connects to the search daemon (not necessarily the same as above)
  server_host = localhost
  server_port = 3312
}

source
{
  # Individual SQL source options
  sql_ranged_throttle = 0  
  sql_range_step = 5000   
  sql_query_post =
}

index
{
  # Index building options
  path = /your-rails-app/db/sphinx/
  docinfo = extern # just leave this alone
  # morphology = stem_en
  stopwords = # /path/to/stopwords.txt
  min_word_len = 1

  # HTML-specific options
  html_strip = 0
  html_index_attrs =
  
  # Enable these if you need wildcard searching. They will slow down indexing significantly.
  min_infix_len = 1    
  #   enable_star = 1 
    
  charset_type = utf-8 # or sbcs (Single Byte Character Set)
  min_word_len = 1
  
  #http://www.sphinxsearch.com/forum/view.html?id=587  
  charset_table = U+FF10..U+FF19->0..9, 0..9, U+FF41..U+FF5A->a..z, U+FF21..U+FF3A->a..z,A..Z->a..z, a..z, U+0149, U+017F, U+0138, U+00DF, U+00FF, U+00C0..U+00D6->U+00E0..U+00F6, U+00E0..U+00F6, U+00D8..U+00DE->U+00F8..U+00FE, U+00F8..U+00FE, U+0100->U+0101, U+0101, U+0102->U+0103, U+0103, U+0104->U+0105, U+0105, U+0106->U+0107, U+0107, U+0108->U+0109, U+0109, U+010A->U+010B, U+010B, U+010C->U+010D, U+010D, U+010E->U+010F, U+010F, U+0110->U+0111, U+0111, U+0112->U+0113, U+0113, U+0114->U+0115, U+0115, U+0116->U+0117, U+0117, U+0118->U+0119, U+0119, U+011A->U+011B, U+011B, U+011C->U+011D, U+011D, U+011E->U+011F, U+011F, U+0130->U+0131, U+0131, U+0132->U+0133, U+0133, U+0134->U+0135, U+0135, U+0136->U+0137, U+0137, U+0139->U+013A, U+013A, U+013B->U+013C, U+013C, U+013D->U+013E, U+013E, U+013F->U+0140, U+0140, U+0141->U+0142, U+0142, U+0143->U+0144, U+0144, U+0145->U+0146, U+0146, U+0147->U+0148, U+0148, U+014A->U+014B, U+014B, U+014C->U+014D, U+014D, U+014E->U+014F, U+014F, U+0150->U+0151, U+0151, U+0152->U+0153, U+0153, U+0154->U+0155, U+0155, U+0156->U+0157, U+0157, U+0158->U+0159, U+0159, U+015A->U+015B, U+015B, U+015C->U+015D, U+015D, U+015E->U+015F, U+015F, U+0160->U+0161, U+0161, U+0162->U+0163, U+0163, U+0164->U+0165, U+0165, U+0166->U+0167, U+0167, U+0168->U+0169, U+0169, U+016A->U+016B, U+016B, U+016C->U+016D, U+016D, U+016E->U+016F, U+016F, U+0170->U+0171, U+0171, U+0172->U+0173, U+0173, U+0174->U+0175, U+0175, U+0176->U+0177, U+0177, U+0178->U+00FF, U+00FF, U+0179->U+017A, U+017A, U+017B->U+017C, U+017C, U+017D->U+017E, U+017E, U+0410..U+042F->U+0430..U+044F, U+0430..U+044F, U+05D0..U+05EA, U+0531..U+0556->U+0561..U+0586, U+0561..U+0587, U+0621..U+063A, U+01B9, U+01BF, U+0640..U+064A, U+0660..U+0669, U+066E, U+066F, U+0671..U+06D3, U+06F0..U+06FF, U+0904..U+0939, U+0958..U+095F, U+0960..U+0963, U+0966..U+096F, U+097B..U+097F, U+0985..U+09B9, U+09CE, U+09DC..U+09E3, U+09E6..U+09EF, U+0A05..U+0A39, U+0A59..U+0A5E, U+0A66..U+0A6F, U+0A85..U+0AB9, U+0AE0..U+0AE3, U+0AE6..U+0AEF, U+0B05..U+0B39, U+0B5C..U+0B61, U+0B66..U+0B6F, U+0B71, U+0B85..U+0BB9, U+0BE6..U+0BF2, U+0C05..U+0C39, U+0C66..U+0C6F, U+0C85..U+0CB9, U+0CDE..U+0CE3, U+0CE6..U+0CEF, U+0D05..U+0D39, U+0D60, U+0D61, U+0D66..U+0D6F, U+0D85..U+0DC6, U+1900..U+1938, U+1946..U+194F, U+A800..U+A805, U+A807..U+A822, U+0386->U+03B1, U+03AC->U+03B1, U+0388->U+03B5, U+03AD->U+03B5, U+0389->U+03B7, U+03AE->U+03B7, U+038A->U+03B9, U+0390->U+03B9, U+03AA->U+03B9, U+03AF->U+03B9, U+03CA->U+03B9, U+038C->U+03BF, U+03CC->U+03BF, U+038E->U+03C5, U+03AB->U+03C5, U+03B0->U+03C5, U+03CB->U+03C5, U+03CD->U+03C5, U+038F->U+03C9, U+03CE->U+03C9, U+03C2->U+03C3, U+0391..U+03A1->U+03B1..U+03C1, U+03A3..U+03A9->U+03C3..U+03C9, U+03B1..U+03C1, U+03C3..U+03C9, U+0E01..U+0E2E, U+0E30..U+0E3A, U+0E40..U+0E45, U+0E47, U+0E50..U+0E59, U+A000..U+A48F, U+4E00..U+9FBF, U+3400..U+4DBF, U+20000..U+2A6DF, U+F900..U+FAFF, U+2F800..U+2FA1F, U+2E80..U+2EFF, U+2F00..U+2FDF, U+3100..U+312F, U+31A0..U+31BF, U+3040..U+309F, U+30A0..U+30FF, U+31F0..U+31FF, U+AC00..U+D7AF, U+1100..U+11FF, U+3130..U+318F, U+A000..U+A48F, U+A490..U+A4CF,
  ngram_len = 1
  ngram_chars = U+4E00..U+9FBF, U+3400..U+4DBF, U+20000..U+2A6DF, U+F900..U+FAFF, U+2F800..U+2FA1F, U+2E80..U+2EFF, U+2F00..U+2FDF, U+3100..U+312F, U+31A0..U+31BF, U+3040..U+309F, U+30A0..U+30FF, U+31F0..U+31FF, U+AC00..U+D7AF, U+1100..U+11FF, U+3130..U+318F, U+A000..U+A48F, U+A490..U+A4CF
}

接下來設定你的 Model 要索引哪些欄位，例如

Class Topic < ActiveRecord::Base
  is_indexed :fields => ['subject', 'content']
end

接著產生實際要用的設定檔。注意到如果你之後有改 model 的 is_indexed，這個設定檔每次都要重新產生(因為裡面的東西是 SQL 指令)。

  rake ultrasphinx:configure

跑索引跟 daemon 很簡單

rake ultrasphinx:index
rake ultrasphinx:daemon:start

至此可以搜尋了:

  @search = Ultrasphinx::Search.new(:query => 'keyword')
  @search.run
  @search.results

如果你要更進一步的搜尋，像是限定 Model 或 Association scoping，就請認真做功課唸Ultrasphinx 文件囉。