page cache, sweeper

Scaling Rails - 第二章 Page Caching
Scaling Rails - 第三章 Cache Expiration
Ruby on Rails Caching Tutorial

要注意的地方:
Sweeper 不僅可以 Observes the Controller 更可以 Observes Models。!!
sweeper 可以使用任何 ActiveRecord 的 callbacks 。
還可以用 controller callbacks，更還可以細到 action level。
ex:
after_posts
before_posts_index

如果觀察物件的object 被觸發了, 但當前的action 並沒有被sweeper 監視, 則呼叫exprie 的function就不會叫了

---

cache my pagination pages?
<br />map.connect 'blog/list/:page',<br /> :controller => 'blog',<br /> :action => 'list',<br /> :requirements => { :page => /\d+/},<br /> :page => nil<br />


Playing nice with Apache/Lighttpd
Clearing out a partial/whole cache

Character entity

wiki Character_entity_reference
HTML character entity

apache: install mod_expire and use

如何向已經安裝好的apache添加一個模塊
使用mod_expires模組來加速網頁瀏覽
Apache Module mod_expires

1. download the apache source
http://httpd.apache.org/download.cgi

2. compile source
<br /> cd modules/metadata/<br /> /YourApachePath/apache/bin/apxs -c mod_expires.c<br /> gcc -shared -o mod_expires.so mod_expires.o -lgdbm<br /> /YourApachePath/apache/bin/apxs -i -A -n mod_expires mod_expires.so<br />
3. edit http.conf
LoadModule expires_module modules/mod_expires.so

and
<br /><IfModule mod_expires.c><br /> ExpiresActive On<br /> ExpiresDefault "access plus 10 days"<br /> ExpiresByType text/css "access plus 1 second"<br /></IfModule><br />

ubuntu 8.10 遇到的問題

1. 因為gcin 造成的一直閃的問題,
我就換成scim了
im-switch -s scim

2. flash 方塊字
將/etc/fonts/conf.avail/49-sansserif.conf
這個檔案刪除即可。

3. opera 和 scim 衝突
sudo apt-get install scim-qtimm
sudo gedit /usr/bin/opera
在第二行添加 export export QT_IM_MODULE=SCIM ，保存後重啟 opera

4.virtualbox 的鳥問題
直接重灌到2.1.0了
http://www.virtualbox.org/wiki/Linux_Downloads

ActiveRecord memo(3)

1. Observer
<br />#可以特別指定, 要觀察誰<br /> class AuditObserver < ActiveRecord::Observer<br /> observe :account, :balance<br /><br /> def after_update(record)<br /> AuditTrail.new(record, "UPDATED")<br /> end<br /> end<br /><br />#然後要在environment 裡設定<br />config.active_record.observers = [:comment_observer, :signup_observer]<br />

2. validate 錯誤時, 可以
<br /> #針對個別屬性errors.add <br /> class User < ActiveRecord::Base<br /> def validate<br /> unless name && name =~ /^\w+$/<br /> errors.add(:name, "is missing or invalid" )<br /> end<br /> end<br /> def validate_on_create<br /> if User.find_by_name(name)<br /> errors.add(:name, "is already being used" )<br /> end<br /> end<br /> end<br /><br /> #針對整個object<br /> def validate<br /> if name.blank? && email.blank?<br /> errors.add_to_base("You must specify a name or an email address" )<br /> end<br /> end<br />

ActiveRecord memo(2)

1. 18.1 p379
<br />#會建立一個可同時在兩個外鍵欄位上搜尋的index, 一般而言便是可以很快找到某個 product_id 所對應的category_id<br />add_index :categories_products, [:product_id, :category_id]<br /><br />#再利用這個index 快速取得此category<br />add_index :categories_products, :category_id<br />

2. 18.3 p384
<br />>> u = User.first<br />=> #<User id: 1, name: "ilakela"><br />>> u.profile.others<br />=> "dddddddddd"<br />>> u.profile.others<br />=> "dddddddddd"<br />>> u.profile.others<br />=> "dddddddddd"<br /><br />#傳回的profile object 結果被cache 了, 所以只撈了一次db<br /> User Load (0.2ms) SELECT * FROM `users` LIMIT 1<br /> Profile Load (0.6ms) SELECT * FROM `profiles` WHERE (`profiles`.user_id = 1) LIMIT 1<br /><br />
3. dependent
<br />#砍上面的, 下面的也砍<br />:dependent => :destroy(or true) <br /><br />#砍上面的, 下面設成foreign key 設成null<br />:dependent => :nullify<br /><br />#砍上面的不理下面的<br />:dependent => :false(or nil)<br />

4 18.3 p389, :finder_sql, and order
<br /> #select A的東西, 卻需要B的條件時<br /> has_many :rails_line_items,<br /> :class_name => "LineItem"<br /> :finder_sql => "select l.* from line_items l, products p" +<br /> "where l.product_id = p.id" +<br /> "and p.title like '%rails%'"<br /><br /> #這樣是先照quantity 的ASC 做排序, 相同時再用unit_price DESC 排序<br /> has_many :line_items, :order => "quantity, unit_price DESC"<br />

5. 18.3 p391 has_many 的一些method, <<, push, replace, clear, uniq(好像拿掉了)

6. 去除重覆的部份
sql distinct
<br /> #unique的動作是在ActiveRecord 做的<br /> has_many :users, :through => :readings, :unique => true<br /><br /> #可以在sql 做好<br /> has_many :users, :through => :readings, :select => "distinct users.*"<br />

7. has_many, extend
<br />#基本<br />#原本<br />class Organization < ActiveRecord::Base<br /> has_many :people do<br /> def find_active<br /> find(:all, :conditions => ["active = ?", true])<br /> end<br /> end<br />end<br /><br />#弄到自己的module<br />module FindActiveExtension<br /> def find_active<br /> find(:all, :conditions => ["active = ?", true])<br /> end<br />end<br /><br />class Organization < ActiveRecord::Base<br /> has_many :people, :extend => FindActiveExtension<br />end<br />#-----------------------------------------------------------<br />#高級技巧 XD<br />#原本的樣子<br />class Project < ActiveRecord::Base<br /> has_many :tasks, :dependent => :delete_all do<br /> def active(reload=false)<br /> @active = nil if reload<br /> @active ||= find(:all, :conditions => "status = 'active'")<br /> end<br /><br /> def inactive(reload=false)<br /> @inactive = nil if reload<br /> @inactive ||= find(:all, :conditions => "status = 'inactive'")<br /> end<br /> end<br />end<br /><br />#利用 extend 的技巧<br />class Project < ActiveRecord::Base<br /> has_many :tasks, :dependent => :delete_all do<br /> memoized_finder :active, "status = 'active'"<br /> memoized_finder :inactive, "status = 'inactive'"<br /> end<br />end<br /><br />#注意他是弄在core module<br />class Module<br /> def memoized_finder(name, conditions=nil)<br /> class_eval <<-STR<br /> def #{name}(reload=false)<br /> @#{name} = nil if reload<br /> @#{name} ||= find(:all, :conditions => #{conditions.inspect})<br /> end<br /> STR<br /> end<br />end<br />

backup restore database

backup up database in hostrails
<br />/usr/bin/mysqldump -h localhost -uUsername -pDbpassword --default-character-set=latin1 database_name > /home/iwakela/filename.sql<br />

MySQL編碼由 latin1 轉 utf8
把 dump 出來的 database.sql 下載回去 .. 用 emEditor（網路上可免費下載，是個支援 utf-8 的編輯器）把 database.sql 打開，

它可以正常識別 utf8 的文字 ..用取代的功能，把 latin1 都取代成 utf8 ，之後直接另存新檔 .. 這時把檔案類型設定儲存成 UTF-8

最後
mysql -uUsername -pDbpassword iwakela_production < earlybirds.sql