环境:ubuntu 10.10 + mysql 5.1 + rails 3.0.3 + ruby 1.9.2
今天创建组合索引时，遇到下面的错误:
Mysql2::Error: Specified key was too long; max key length is 1000 bytes: CREATE UNIQUE INDEX `unique_users_name_password` ON `users` (`name`, `password`)
问题重现:
表结构:(数据库,表,字段都是utf-8 编码,myisam引擎)
users: name: varchar(255) password: varchar(255)
Rails创建索引:
add_index :users , [:name,:password] , :unique=>true , :name=>"unique_users_name_password" # mysql 唯一索引可以指定多个字段
执行就 Error 了 ,
Google 后 ，得到是 myisam 表组合索引 有长度限制 , 总长度不能 超过 1000 bytes
计算下上面的 总长度(bytes)
utf8 编码 : 1 char = 3 bytes
255 * 3 + 255 * 3 = 1530 bytes
果然大于1000 了 ,修改 name 的字段长度:
change_column :users ,:name , :string , :limit => 100
再建索引 就 ok了……
那么 表改为 innodb 引擎呢 ,不error 了 ,但是 会抱下面的warning
warning：Specified key was too long;max key length is 767 bytes.why?
原来 innodb表的组合索引的长度 是 767 bytes ， 比 myisam 的还少 ，但是 innodb的可以顺利 建索引，超过767长度的部分 建不被索引，前面的取 前缀索引 ,这里 要注意!
建议;
1,表 设置为 innodb
2,建字段时，一定要根据实际情况,限制长度,在 rails migration中就是 加 :limit 参数
see:
http://blog.fesite.com/2009/02/09/mysql-specified-key-was-too-long-max-key-length-is-1000-bytes/
http://samyubw.blog.51cto.com/978243/223773
环境:ruby 1.9.2 + rails 3.0.3 + nb 6.9.1 + ubuntu 10.10
nb debug rails 3.0 还没有跟上,不可以debug rails 3.0项目了，网上也有很多人遇到,可能出现下面这个异常:
Uncaught exception: no such file to load -- script/rails我有一个解决办法,把你要debug的项目path直接写进去,
需要用到的gem:
ruby-debug-base19 (0.11.24) ruby-debug-ide (0.4.9) linecache19 (0.5.11)
如果是debug test file 的话,还需要 test-unit
wxianfeng@ubuntu:~$ gem list ruby- *** LOCAL GEMS *** ruby-debug-base19 (0.11.24) ruby-debug-ide (0.4.9)
wxianfeng@ubuntu:~$ gem list line *** LOCAL GEMS *** linecache19 (0.5.11)
wxianfeng@ubuntu:~$ gem list test *** LOCAL GEMS *** test-unit (2.1.2)
当前rvm环境;
wxianfeng@ubuntu:~$ rvm info ruby-1.9.2-p0: system: uname: "Linux ubuntu 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC 2010 i686 GNU/Linux" bash: "/bin/bash => GNU bash, version 4.1.5(1)-release (i686-pc-linux-gnu)" zsh: " => not installed" rvm: version: "rvm 1.1.0 by Wayne E. Seguin (wayneeseguin@gmail.com) [http://rvm.beginrescueend.com/]" ruby: interpreter: "ruby" version: "1.9.2p0" date: "2010-08-18" platform: "i686-linux" patchlevel: "2010-08-18 revision 29036" full_version: "ruby 1.9.2p0 (2010-08-18 revision 29036) [i686-linux]" homes: gem: "/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0" ruby: "/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0" binaries: ruby: "/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0/bin/ruby" irb: "/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0/bin/irb" gem: "/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0/bin/gem" rake: "/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0/bin/rake" environment: PATH: "/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0/bin:/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0@global/bin:/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0/bin:/home/wxianfeng/.rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/system/mysql/bin:/usr/local/system/jdk1.6.0_22/bin" GEM_HOME: "/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0" GEM_PATH: "/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0:/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0@global" MY_RUBY_HOME: "/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0" IRBRC: "/home/wxianfeng/.rvm/rubies/ruby-1.9.2-p0/.irbrc" RUBYOPT: "" gemset: ""
注意把netbeans的 gem_home , gem_path 设置为 当前 rvm 对应的 gem_home , gem_path , 设置gem_path 时 nb 默认 .rvm 目录不显示，需要直接在 对话框中输入路径
最后修改
/home/wxianfeng/.rvm/gems/ruby-1.9.2-p0/gems/ruby-debug-ide-0.4.9/lib/ruby-debug-ide.rb
大概 110 行
path = "/usr/local/system/projects/entos/ent_os/script/rails" bt = debug_load(path, options.stop, options.load_mode) # bt = debug_load(Debugger::PROG_SCRIPT, options.stop, options.load_mode)
注释一行,添加两行
把你需要调试的项目 set as main project ,然后 debug main project !
ok~!
如果你需要debug 单个ruby 文件 ， 那么 需要改回来 ， 这里注意.